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 $213.64   5.811%   $226.0546   $226.05   $226.05   $226.10  
  Purchase #2 $193.59   13.407%   $219.5446   $219.54   $219.55   $219.50  
  Purchase #3 $74.32   3.755%   $77.1107   $77.11   $77.10   $77.10  
  Purchase #4 $178.55   3.487%   $184.776   $184.78   $184.80   $184.80  
  Purchase #5 $207.41   10.476%   $229.1383   $229.14   $229.15   $229.10  
  Purchase #6 $96.40   7.303%   $103.4401   $103.44   $103.45   $103.40  
  Purchase #7 $21.48   8.795%   $23.3692   $23.37   $23.35   $23.40  
  7 purchase totals = $985.39       $1,063.4335   $1,063.43   $1,063.45   $1,063.40