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 $211.46   7.355%   $227.0129   $227.01   $227.00   $227.00  
  Purchase #2 $221.37   7.522%   $238.0215   $238.02   $238.00   $238.00  
  Purchase #3 $218.28   7.604%   $234.878   $234.88   $234.90   $234.90  
  Purchase #4 $99.55   5.351%   $104.8769   $104.88   $104.90   $104.90  
  Purchase #5 $53.99   9.232%   $58.9744   $58.97   $58.95   $59.00  
  Purchase #6 $123.35   7.263%   $132.3089   $132.31   $132.30   $132.30  
  Purchase #7 $108.91   3.591%   $112.821   $112.82   $112.80   $112.80  
  7 purchase totals = $1,036.91       $1,108.8936   $1,108.89   $1,108.85   $1,108.90