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 $224.96   7.552%   $241.949   $241.95   $241.95   $241.90  
  Purchase #2 $111.79   10.271%   $123.272   $123.27   $123.25   $123.30  
  Purchase #3 $165.35   5.809%   $174.9552   $174.96   $174.95   $175.00  
  Purchase #4 $202.69   6.465%   $215.7939   $215.79   $215.80   $215.80  
  Purchase #5 $63.61   11.363%   $70.838   $70.84   $70.85   $70.80  
  Purchase #6 $183.94   11.156%   $204.4603   $204.46   $204.45   $204.50  
  Purchase #7 $138.46   5.610%   $146.2276   $146.23   $146.25   $146.20  
  7 purchase totals = $1,090.80       $1,177.4960   $1,177.50   $1,177.50   $1,177.50