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 $82.37   12.683%   $92.817   $92.82   $92.80   $92.80  
  Purchase #2 $154.93   4.194%   $161.4278   $161.43   $161.45   $161.40  
  Purchase #3 $85.35   3.277%   $88.1469   $88.15   $88.15   $88.10  
  Purchase #4 $180.50   13.533%   $204.9271   $204.93   $204.95   $204.90  
  Purchase #5 $54.73   9.152%   $59.7389   $59.74   $59.75   $59.70  
  Purchase #6 $190.57   11.693%   $212.8534   $212.85   $212.85   $212.90  
  Purchase #7 $226.73   9.813%   $248.979   $248.98   $249.00   $249.00  
  7 purchase totals = $975.18       $1,068.8901   $1,068.90   $1,068.95   $1,068.80