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 $151.82   7.120%   $162.6296   $162.63   $162.65   $162.60  
  Purchase #2 $195.83   4.522%   $204.6854   $204.69   $204.70   $204.70  
  Purchase #3 $28.70   13.841%   $32.6724   $32.67   $32.65   $32.70  
  Purchase #4 $151.96   4.535%   $158.8514   $158.85   $158.85   $158.90  
  Purchase #5 $133.81   10.532%   $147.9029   $147.90   $147.90   $147.90  
  Purchase #6 $191.90   7.198%   $205.713   $205.71   $205.70   $205.70  
  Purchase #7 $86.98   8.107%   $94.0315   $94.03   $94.05   $94.00  
  7 purchase totals = $941.00       $1,006.4862   $1,006.48   $1,006.50   $1,006.50