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 $97.46   6.340%   $103.639   $103.64   $103.65   $103.60  
  Purchase #2 $190.44   11.456%   $212.2568   $212.26   $212.25   $212.30  
  Purchase #3 $116.81   11.531%   $130.2794   $130.28   $130.30   $130.30  
  Purchase #4 $226.33   8.603%   $245.8012   $245.80   $245.80   $245.80  
  Purchase #5 $75.45   8.153%   $81.6014   $81.60   $81.60   $81.60  
  Purchase #6 $13.43   5.220%   $14.131   $14.13   $14.15   $14.10  
  Purchase #7 $54.74   10.680%   $60.5862   $60.59   $60.60   $60.60  
  7 purchase totals = $774.66       $848.2950   $848.30   $848.35   $848.30