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 $51.71   13.328%   $58.6019   $58.60   $58.60   $58.60  
  Purchase #2 $208.96   10.350%   $230.5874   $230.59   $230.60   $230.60  
  Purchase #3 $206.97   12.252%   $232.328   $232.33   $232.35   $232.30  
  Purchase #4 $222.45   4.336%   $232.0954   $232.10   $232.10   $232.10  
  Purchase #5 $153.91   4.694%   $161.1345   $161.13   $161.15   $161.10  
  Purchase #6 $216.87   13.143%   $245.3732   $245.37   $245.35   $245.40  
  Purchase #7 $47.30   5.530%   $49.9157   $49.92   $49.90   $49.90  
  7 purchase totals = $1,108.17       $1,210.0361   $1,210.04   $1,210.05   $1,210.00