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 $46.51   11.834%   $52.014   $52.01   $52.00   $52.00  
  Purchase #2 $195.43   3.217%   $201.717   $201.72   $201.70   $201.70  
  Purchase #3 $197.93   11.399%   $220.492   $220.49   $220.50   $220.50  
  Purchase #4 $216.36   7.314%   $232.1846   $232.18   $232.20   $232.20  
  Purchase #5 $77.74   13.553%   $88.2761   $88.28   $88.30   $88.30  
  Purchase #6 $90.91   12.767%   $102.5165   $102.52   $102.50   $102.50  
  Purchase #7 $76.51   12.241%   $85.8756   $85.88   $85.90   $85.90  
  7 purchase totals = $901.39       $983.0758   $983.08   $983.10   $983.10