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 $201.66   11.635%   $225.1231   $225.12   $225.10   $225.10  
  Purchase #2 $209.47   5.189%   $220.3394   $220.34   $220.35   $220.30  
  Purchase #3 $54.73   10.294%   $60.3639   $60.36   $60.35   $60.40  
  Purchase #4 $68.49   3.727%   $71.0426   $71.04   $71.05   $71.00  
  Purchase #5 $23.88   11.139%   $26.54   $26.54   $26.55   $26.50  
  Purchase #6 $198.55   8.345%   $215.119   $215.12   $215.10   $215.10  
  Purchase #7 $244.94   12.821%   $276.3438   $276.34   $276.35   $276.30  
  7 purchase totals = $1,001.72       $1,094.8718   $1,094.86   $1,094.85   $1,094.70