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 $105.98   12.559%   $119.29   $119.29   $119.30   $119.30  
  Purchase #2 $161.41   10.130%   $177.7608   $177.76   $177.75   $177.80  
  Purchase #3 $194.86   6.220%   $206.9803   $206.98   $207.00   $207.00  
  Purchase #4 $62.41   10.399%   $68.9   $68.90   $68.90   $68.90  
  Purchase #5 $238.85   3.307%   $246.7488   $246.75   $246.75   $246.70  
  Purchase #6 $180.33   12.808%   $203.4267   $203.43   $203.45   $203.40  
  Purchase #7 $134.90   9.874%   $148.22   $148.22   $148.20   $148.20  
  7 purchase totals = $1,078.74       $1,171.3266   $1,171.33   $1,171.35   $1,171.30