Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $245.86   9.446%   $269.0839   $269.08   $269.10   $269.10  
  Purchase #2 $160.67   4.373%   $167.6961   $167.70   $167.70   $167.70  
  Purchase #3 $176.88   10.236%   $194.9854   $194.99   $195.00   $195.00  
  Purchase #4 $95.27   11.268%   $106.005   $106.01   $106.00   $106.00  
  Purchase #5 $162.37   12.183%   $182.1515   $182.15   $182.15   $182.20  
  Purchase #6 $128.43   11.163%   $142.7666   $142.77   $142.75   $142.80  
  Purchase #7 $196.88   3.751%   $204.265   $204.27   $204.25   $204.30  
  7 purchase totals = $1,166.36       $1,266.9535   $1,266.97   $1,266.95   $1,267.10