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 $114.26   6.823%   $122.056   $122.06   $122.05   $122.10  
  Purchase #2 $96.35   6.132%   $102.2582   $102.26   $102.25   $102.30  
  Purchase #3 $53.28   8.517%   $57.8179   $57.82   $57.80   $57.80  
  Purchase #4 $161.91   4.698%   $169.5165   $169.52   $169.50   $169.50  
  Purchase #5 $47.93   11.800%   $53.5857   $53.59   $53.60   $53.60  
  Purchase #6 $222.37   11.328%   $247.5601   $247.56   $247.55   $247.60  
  Purchase #7 $140.76   10.245%   $155.1809   $155.18   $155.20   $155.20  
  7 purchase totals = $836.86       $907.9753   $907.99   $907.95   $908.10