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 $59.87   4.776%   $62.7294   $62.73   $62.75   $62.70  
  Purchase #2 $83.64   9.551%   $91.6285   $91.63   $91.65   $91.60  
  Purchase #3 $198.65   7.873%   $214.2897   $214.29   $214.30   $214.30  
  Purchase #4 $74.87   8.264%   $81.0573   $81.06   $81.05   $81.10  
  Purchase #5 $135.28   5.429%   $142.6244   $142.62   $142.60   $142.60  
  Purchase #6 $86.61   11.570%   $96.6308   $96.63   $96.65   $96.60  
  Purchase #7 $57.32   12.298%   $64.3692   $64.37   $64.35   $64.40  
  7 purchase totals = $696.24       $753.3293   $753.33   $753.35   $753.30