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 $92.36   3.262%   $95.3728   $95.37   $95.35   $95.40  
  Purchase #2 $184.85   12.776%   $208.4664   $208.47   $208.45   $208.50  
  Purchase #3 $211.72   5.863%   $224.1331   $224.13   $224.15   $224.10  
  Purchase #4 $121.37   9.213%   $132.5518   $132.55   $132.55   $132.60  
  Purchase #5 $51.65   3.206%   $53.3059   $53.31   $53.30   $53.30  
  Purchase #6 $219.50   11.643%   $245.0564   $245.06   $245.05   $245.10  
  Purchase #7 $240.42   4.718%   $251.763   $251.76   $251.75   $251.80  
  7 purchase totals = $1,121.87       $1,210.6494   $1,210.65   $1,210.60   $1,210.80