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 $114.66   10.794%   $127.0364   $127.04   $127.05   $127.00  
  Purchase #2 $205.33   11.284%   $228.4994   $228.50   $228.50   $228.50  
  Purchase #3 $13.52   4.805%   $14.1696   $14.17   $14.15   $14.20  
  Purchase #4 $51.98   5.526%   $54.8524   $54.85   $54.85   $54.90  
  Purchase #5 $187.26   9.502%   $205.0534   $205.05   $205.05   $205.10  
  Purchase #6 $196.67   6.661%   $209.7702   $209.77   $209.75   $209.80  
  Purchase #7 $90.45   5.754%   $95.6545   $95.65   $95.65   $95.70  
  7 purchase totals = $859.87       $935.0359   $935.03   $935.00   $935.20