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 $62.86   4.747%   $65.844   $65.84   $65.85   $65.80  
  Purchase #2 $229.53   3.185%   $236.8405   $236.84   $236.85   $236.80  
  Purchase #3 $93.56   5.736%   $98.9266   $98.93   $98.95   $98.90  
  Purchase #4 $233.36   4.380%   $243.5812   $243.58   $243.60   $243.60  
  Purchase #5 $199.87   6.536%   $212.9335   $212.93   $212.95   $212.90  
  Purchase #6 $109.82   8.562%   $119.2228   $119.22   $119.20   $119.20  
  Purchase #7 $220.49   7.344%   $236.6828   $236.68   $236.70   $236.70  
  7 purchase totals = $1,149.49       $1,214.0314   $1,214.02   $1,214.10   $1,213.90