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 $187.46   7.251%   $201.0527   $201.05   $201.05   $201.10  
  Purchase #2 $204.89   13.258%   $232.0543   $232.05   $232.05   $232.10  
  Purchase #3 $38.95   10.691%   $43.1141   $43.11   $43.10   $43.10  
  Purchase #4 $138.52   13.826%   $157.6718   $157.67   $157.65   $157.70  
  Purchase #5 $106.52   12.341%   $119.6656   $119.67   $119.65   $119.70  
  Purchase #6 $201.48   5.343%   $212.2451   $212.25   $212.25   $212.20  
  Purchase #7 $63.27   11.782%   $70.7245   $70.72   $70.70   $70.70  
  7 purchase totals = $941.09       $1,036.5281   $1,036.52   $1,036.45   $1,036.60