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 $62.54   5.416%   $65.9272   $65.93   $65.95   $65.90  
  Purchase #2 $85.62   12.489%   $96.3131   $96.31   $96.30   $96.30  
  Purchase #3 $59.32   4.770%   $62.1496   $62.15   $62.15   $62.10  
  Purchase #4 $150.61   3.185%   $155.4069   $155.41   $155.40   $155.40  
  Purchase #5 $179.96   8.334%   $194.9579   $194.96   $194.95   $195.00  
  Purchase #6 $180.30   7.781%   $194.3291   $194.33   $194.35   $194.30  
  Purchase #7 $238.79   11.865%   $267.1224   $267.12   $267.10   $267.10  
  7 purchase totals = $957.14       $1,036.2062   $1,036.21   $1,036.20   $1,036.10