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 $73.25   3.242%   $75.6248   $75.62   $75.60   $75.60  
  Purchase #2 $178.44   7.167%   $191.2288   $191.23   $191.25   $191.20  
  Purchase #3 $190.59   5.740%   $201.5299   $201.53   $201.55   $201.50  
  Purchase #4 $155.75   10.789%   $172.5539   $172.55   $172.55   $172.60  
  Purchase #5 $210.39   12.407%   $236.4931   $236.49   $236.50   $236.50  
  Purchase #6 $111.48   13.812%   $126.8776   $126.88   $126.90   $126.90  
  Purchase #7 $96.80   5.362%   $101.9904   $101.99   $102.00   $102.00  
  7 purchase totals = $1,016.70       $1,106.2985   $1,106.29   $1,106.35   $1,106.30