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 $88.54   4.640%   $92.6483   $92.65   $92.65   $92.60  
  Purchase #2 $216.86   5.252%   $228.2495   $228.25   $228.25   $228.20  
  Purchase #3 $46.75   13.276%   $52.9565   $52.96   $52.95   $53.00  
  Purchase #4 $58.66   8.300%   $63.5288   $63.53   $63.55   $63.50  
  Purchase #5 $226.97   12.251%   $254.7761   $254.78   $254.80   $254.80  
  Purchase #6 $171.52   13.263%   $194.2687   $194.27   $194.25   $194.30  
  Purchase #7 $83.73   12.616%   $94.2934   $94.29   $94.30   $94.30  
  7 purchase totals = $893.03       $980.7213   $980.73   $980.75   $980.70