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 $62.38   4.116%   $64.9476   $64.95   $64.95   $64.90  
  Purchase #2 $70.98   3.306%   $73.3266   $73.33   $73.35   $73.30  
  Purchase #3 $210.70   9.718%   $231.1758   $231.18   $231.20   $231.20  
  Purchase #4 $134.63   8.406%   $145.947   $145.95   $145.95   $145.90  
  Purchase #5 $210.53   4.155%   $219.2775   $219.28   $219.30   $219.30  
  Purchase #6 $224.85   8.177%   $243.236   $243.24   $243.25   $243.20  
  Purchase #7 $183.70   10.277%   $202.5788   $202.58   $202.60   $202.60  
  7 purchase totals = $1,097.77       $1,180.4893   $1,180.51   $1,180.60   $1,180.40