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 $194.98   5.142%   $205.0059   $205.01   $205.00   $205.00  
  Purchase #2 $116.59   7.437%   $125.2608   $125.26   $125.25   $125.30  
  Purchase #3 $151.32   5.238%   $159.2461   $159.25   $159.25   $159.20  
  Purchase #4 $67.50   8.494%   $73.2335   $73.23   $73.25   $73.20  
  Purchase #5 $207.65   13.541%   $235.7679   $235.77   $235.75   $235.80  
  Purchase #6 $196.42   10.629%   $217.2975   $217.30   $217.30   $217.30  
  Purchase #7 $6.46   5.301%   $6.8024   $6.80   $6.80   $6.80  
  7 purchase totals = $940.92       $1,022.6141   $1,022.62   $1,022.60   $1,022.60