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 $82.48   5.174%   $86.7475   $86.75   $86.75   $86.70  
  Purchase #2 $163.68   11.742%   $182.8993   $182.90   $182.90   $182.90  
  Purchase #3 $197.51   11.846%   $220.907   $220.91   $220.90   $220.90  
  Purchase #4 $227.41   4.750%   $238.212   $238.21   $238.20   $238.20  
  Purchase #5 $181.54   11.484%   $202.3881   $202.39   $202.40   $202.40  
  Purchase #6 $71.55   6.619%   $76.2859   $76.29   $76.30   $76.30  
  Purchase #7 $53.91   3.402%   $55.744   $55.74   $55.75   $55.70  
  7 purchase totals = $978.08       $1,063.1838   $1,063.19   $1,063.20   $1,063.10