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 $56.99   10.372%   $62.901   $62.90   $62.90   $62.90  
  Purchase #2 $66.47   13.248%   $75.2759   $75.28   $75.30   $75.30  
  Purchase #3 $212.61   10.818%   $235.6101   $235.61   $235.60   $235.60  
  Purchase #4 $186.33   12.428%   $209.4871   $209.49   $209.50   $209.50  
  Purchase #5 $60.69   8.178%   $65.6532   $65.65   $65.65   $65.70  
  Purchase #6 $61.44   13.699%   $69.8567   $69.86   $69.85   $69.90  
  Purchase #7 $6.68   13.364%   $7.5727   $7.57   $7.55   $7.60  
  7 purchase totals = $651.21       $726.3567   $726.36   $726.35   $726.50