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 $58.94   5.267%   $62.0444   $62.04   $62.05   $62.00  
  Purchase #2 $142.37   6.130%   $151.0973   $151.10   $151.10   $151.10  
  Purchase #3 $139.67   9.563%   $153.0266   $153.03   $153.05   $153.00  
  Purchase #4 $188.33   12.717%   $212.2799   $212.28   $212.30   $212.30  
  Purchase #5 $226.87   3.399%   $234.5813   $234.58   $234.60   $234.60  
  Purchase #6 $57.98   11.836%   $64.8425   $64.84   $64.85   $64.80  
  Purchase #7 $228.47   4.826%   $239.496   $239.50   $239.50   $239.50  
  7 purchase totals = $1,042.63       $1,117.3680   $1,117.37   $1,117.45   $1,117.30