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 $219.89   7.323%   $235.9925   $235.99   $236.00   $236.00  
  Purchase #2 $217.63   6.276%   $231.2885   $231.29   $231.30   $231.30  
  Purchase #3 $18.61   9.250%   $20.3314   $20.33   $20.35   $20.30  
  Purchase #4 $167.51   11.779%   $187.241   $187.24   $187.25   $187.20  
  Purchase #5 $249.52   3.439%   $258.101   $258.10   $258.10   $258.10  
  Purchase #6 $207.42   3.635%   $214.9597   $214.96   $214.95   $215.00  
  Purchase #7 $91.29   9.154%   $99.6467   $99.65   $99.65   $99.60  
  7 purchase totals = $1,171.87       $1,247.5608   $1,247.56   $1,247.60   $1,247.50