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 $91.52   3.532%   $94.7525   $94.75   $94.75   $94.80  
  Purchase #2 $228.28   5.369%   $240.5364   $240.54   $240.55   $240.50  
  Purchase #3 $238.45   6.771%   $254.5954   $254.60   $254.60   $254.60  
  Purchase #4 $29.83   11.744%   $33.3332   $33.33   $33.35   $33.30  
  Purchase #5 $112.47   11.739%   $125.6729   $125.67   $125.65   $125.70  
  Purchase #6 $57.73   7.390%   $61.9962   $62.00   $62.00   $62.00  
  Purchase #7 $146.79   6.724%   $156.6602   $156.66   $156.65   $156.70  
  7 purchase totals = $905.07       $967.5468   $967.55   $967.55   $967.60