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 $232.26   13.761%   $264.2213   $264.22   $264.20   $264.20  
  Purchase #2 $205.69   10.159%   $226.586   $226.59   $226.60   $226.60  
  Purchase #3 $189.61   12.278%   $212.8903   $212.89   $212.90   $212.90  
  Purchase #4 $34.78   6.625%   $37.0842   $37.08   $37.10   $37.10  
  Purchase #5 $27.98   8.215%   $30.2786   $30.28   $30.30   $30.30  
  Purchase #6 $247.28   8.583%   $268.504   $268.50   $268.50   $268.50  
  Purchase #7 $87.38   7.620%   $94.0384   $94.04   $94.05   $94.00  
  7 purchase totals = $1,024.98       $1,133.6028   $1,133.60   $1,133.65   $1,133.60