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 $96.71   9.108%   $105.5183   $105.52   $105.50   $105.50  
  Purchase #2 $112.39   4.419%   $117.3565   $117.36   $117.35   $117.40  
  Purchase #3 $66.96   12.568%   $75.3755   $75.38   $75.40   $75.40  
  Purchase #4 $147.84   3.716%   $153.3337   $153.33   $153.35   $153.30  
  Purchase #5 $184.45   10.408%   $203.6476   $203.65   $203.65   $203.60  
  Purchase #6 $59.99   8.737%   $65.2313   $65.23   $65.25   $65.20  
  Purchase #7 $207.83   11.834%   $232.4246   $232.42   $232.40   $232.40  
  7 purchase totals = $876.17       $952.8875   $952.89   $952.90   $952.80