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 $44.40   5.509%   $46.846   $46.85   $46.85   $46.80  
  Purchase #2 $183.41   11.745%   $204.9515   $204.95   $204.95   $205.00  
  Purchase #3 $116.45   8.623%   $126.4915   $126.49   $126.50   $126.50  
  Purchase #4 $55.88   12.377%   $62.7963   $62.80   $62.80   $62.80  
  Purchase #5 $237.41   3.586%   $245.9235   $245.92   $245.90   $245.90  
  Purchase #6 $23.42   12.583%   $26.3669   $26.37   $26.35   $26.40  
  Purchase #7 $146.94   5.698%   $155.3126   $155.31   $155.30   $155.30  
  7 purchase totals = $807.91       $868.6883   $868.69   $868.65   $868.70