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 $72.36   4.754%   $75.8   $75.80   $75.80   $75.80  
  Purchase #2 $212.39   8.242%   $229.8952   $229.90   $229.90   $229.90  
  Purchase #3 $131.97   10.301%   $145.5642   $145.56   $145.55   $145.60  
  Purchase #4 $238.44   12.534%   $268.3261   $268.33   $268.35   $268.30  
  Purchase #5 $85.49   12.797%   $96.4302   $96.43   $96.45   $96.40  
  Purchase #6 $47.81   5.594%   $50.4845   $50.48   $50.50   $50.50  
  Purchase #7 $209.81   12.797%   $236.6594   $236.66   $236.65   $236.70  
  7 purchase totals = $998.27       $1,103.1596   $1,103.16   $1,103.20   $1,103.20