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 $148.77   4.762%   $155.8544   $155.85   $155.85   $155.90  
  Purchase #2 $188.96   3.647%   $195.8514   $195.85   $195.85   $195.90  
  Purchase #3 $211.91   8.838%   $230.6386   $230.64   $230.65   $230.60  
  Purchase #4 $68.96   3.544%   $71.4039   $71.40   $71.40   $71.40  
  Purchase #5 $216.60   3.674%   $224.5579   $224.56   $224.55   $224.60  
  Purchase #6 $109.52   4.330%   $114.2622   $114.26   $114.25   $114.30  
  Purchase #7 $146.81   4.586%   $153.5427   $153.54   $153.55   $153.50  
  7 purchase totals = $1,091.53       $1,146.1111   $1,146.10   $1,146.10   $1,146.20