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 $87.58   5.394%   $92.3041   $92.30   $92.30   $92.30  
  Purchase #2 $190.49   8.247%   $206.1997   $206.20   $206.20   $206.20  
  Purchase #3 $170.60   3.492%   $176.5574   $176.56   $176.55   $176.60  
  Purchase #4 $211.67   12.133%   $237.3519   $237.35   $237.35   $237.40  
  Purchase #5 $168.32   9.411%   $184.1606   $184.16   $184.15   $184.20  
  Purchase #6 $148.95   13.810%   $169.52   $169.52   $169.50   $169.50  
  Purchase #7 $66.30   11.388%   $73.8502   $73.85   $73.85   $73.90  
  7 purchase totals = $1,043.91       $1,139.9439   $1,139.94   $1,139.90   $1,140.10