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 $112.87   4.191%   $117.6004   $117.60   $117.60   $117.60  
  Purchase #2 $227.56   6.784%   $242.9977   $243.00   $243.00   $243.00  
  Purchase #3 $70.78   7.485%   $76.0779   $76.08   $76.10   $76.10  
  Purchase #4 $185.56   6.631%   $197.8645   $197.86   $197.85   $197.90  
  Purchase #5 $182.97   6.151%   $194.2245   $194.22   $194.20   $194.20  
  Purchase #6 $211.66   3.448%   $218.958   $218.96   $218.95   $219.00  
  Purchase #7 $71.52   5.140%   $75.1961   $75.20   $75.20   $75.20  
  7 purchase totals = $1,062.92       $1,122.9191   $1,122.92   $1,122.90   $1,123.00