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 $191.86   6.698%   $204.7108   $204.71   $204.70   $204.70  
  Purchase #2 $48.75   13.439%   $55.3015   $55.30   $55.30   $55.30  
  Purchase #3 $147.54   5.467%   $155.606   $155.61   $155.60   $155.60  
  Purchase #4 $47.52   6.578%   $50.6459   $50.65   $50.65   $50.60  
  Purchase #5 $191.26   5.503%   $201.785   $201.79   $201.80   $201.80  
  Purchase #6 $145.69   8.111%   $157.5069   $157.51   $157.50   $157.50  
  Purchase #7 $41.52   5.504%   $43.8053   $43.81   $43.80   $43.80  
  7 purchase totals = $814.14       $869.3614   $869.38   $869.35   $869.30