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 $48.43   11.871%   $54.1791   $54.18   $54.20   $54.20  
  Purchase #2 $63.72   6.772%   $68.0351   $68.04   $68.05   $68.00  
  Purchase #3 $223.96   8.754%   $243.5655   $243.57   $243.55   $243.60  
  Purchase #4 $239.36   3.192%   $247.0004   $247.00   $247.00   $247.00  
  Purchase #5 $112.72   5.281%   $118.6727   $118.67   $118.65   $118.70  
  Purchase #6 $132.47   8.500%   $143.73   $143.73   $143.75   $143.70  
  Purchase #7 $195.61   12.487%   $220.0358   $220.04   $220.05   $220.00  
  7 purchase totals = $1,016.27       $1,095.2186   $1,095.23   $1,095.25   $1,095.20