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 $87.44   8.742%   $95.084   $95.08   $95.10   $95.10  
  Purchase #2 $138.34   5.784%   $146.3416   $146.34   $146.35   $146.30  
  Purchase #3 $119.74   13.247%   $135.602   $135.60   $135.60   $135.60  
  Purchase #4 $112.75   7.814%   $121.5603   $121.56   $121.55   $121.60  
  Purchase #5 $238.65   10.201%   $262.9947   $262.99   $263.00   $263.00  
  Purchase #6 $73.94   4.268%   $77.0958   $77.10   $77.10   $77.10  
  Purchase #7 $101.65   5.171%   $106.9063   $106.91   $106.90   $106.90  
  7 purchase totals = $872.51       $945.5847   $945.58   $945.60   $945.60