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 $59.36   3.387%   $61.3705   $61.37   $61.35   $61.40  
  Purchase #2 $96.98   4.781%   $101.6166   $101.62   $101.60   $101.60  
  Purchase #3 $44.86   7.647%   $48.2904   $48.29   $48.30   $48.30  
  Purchase #4 $93.55   4.833%   $98.0713   $98.07   $98.05   $98.10  
  Purchase #5 $108.85   11.566%   $121.4396   $121.44   $121.45   $121.40  
  Purchase #6 $115.57   6.600%   $123.1976   $123.20   $123.20   $123.20  
  Purchase #7 $234.85   4.327%   $245.012   $245.01   $245.00   $245.00  
  7 purchase totals = $754.02       $798.9980   $799.00   $798.95   $799.00