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 $90.52   5.781%   $95.753   $95.75   $95.75   $95.80  
  Purchase #2 $213.44   13.661%   $242.598   $242.60   $242.60   $242.60  
  Purchase #3 $56.35   7.702%   $60.6901   $60.69   $60.70   $60.70  
  Purchase #4 $16.36   13.555%   $18.5776   $18.58   $18.60   $18.60  
  Purchase #5 $218.54   11.730%   $244.1747   $244.17   $244.15   $244.20  
  Purchase #6 $187.58   7.791%   $202.1944   $202.19   $202.20   $202.20  
  Purchase #7 $89.91   5.363%   $94.7319   $94.73   $94.75   $94.70  
  7 purchase totals = $872.70       $958.7197   $958.71   $958.75   $958.80