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 $57.33   7.319%   $61.526   $61.53   $61.55   $61.50  
  Purchase #2 $180.32   5.184%   $189.6678   $189.67   $189.65   $189.70  
  Purchase #3 $211.84   7.159%   $227.0056   $227.01   $227.00   $227.00  
  Purchase #4 $187.98   3.346%   $194.2698   $194.27   $194.25   $194.30  
  Purchase #5 $246.50   6.712%   $263.0451   $263.05   $263.05   $263.00  
  Purchase #6 $76.72   13.728%   $87.2521   $87.25   $87.25   $87.30  
  Purchase #7 $150.83   7.651%   $162.37   $162.37   $162.35   $162.40  
  7 purchase totals = $1,111.52       $1,185.1364   $1,185.15   $1,185.10   $1,185.20