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 $86.42   9.649%   $94.7587   $94.76   $94.75   $94.80  
  Purchase #2 $204.52   3.604%   $211.8909   $211.89   $211.90   $211.90  
  Purchase #3 $210.69   4.699%   $220.5903   $220.59   $220.60   $220.60  
  Purchase #4 $209.53   9.624%   $229.6952   $229.70   $229.70   $229.70  
  Purchase #5 $155.83   8.852%   $169.6241   $169.62   $169.60   $169.60  
  Purchase #6 $43.93   11.250%   $48.8721   $48.87   $48.85   $48.90  
  Purchase #7 $248.71   5.753%   $263.0183   $263.02   $263.00   $263.00  
  7 purchase totals = $1,159.63       $1,238.4496   $1,238.45   $1,238.40   $1,238.50