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 $186.65   4.450%   $194.9559   $194.96   $194.95   $195.00  
  Purchase #2 $126.89   6.104%   $134.6354   $134.64   $134.65   $134.60  
  Purchase #3 $243.68   12.114%   $273.1994   $273.20   $273.20   $273.20  
  Purchase #4 $53.90   10.764%   $59.7018   $59.70   $59.70   $59.70  
  Purchase #5 $229.48   4.659%   $240.1715   $240.17   $240.15   $240.20  
  Purchase #6 $176.94   10.198%   $194.9843   $194.98   $195.00   $195.00  
  Purchase #7 $135.80   8.167%   $146.8908   $146.89   $146.90   $146.90  
  7 purchase totals = $1,153.34       $1,244.5391   $1,244.54   $1,244.55   $1,244.60