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 $67.93   6.114%   $72.0832   $72.08   $72.10   $72.10  
  Purchase #2 $211.55   11.685%   $236.2696   $236.27   $236.25   $236.30  
  Purchase #3 $13.40   4.283%   $13.9739   $13.97   $13.95   $14.00  
  Purchase #4 $133.34   5.760%   $141.0204   $141.02   $141.00   $141.00  
  Purchase #5 $230.37   6.262%   $244.7958   $244.80   $244.80   $244.80  
  Purchase #6 $241.70   4.468%   $252.4992   $252.50   $252.50   $252.50  
  Purchase #7 $221.32   8.537%   $240.2141   $240.21   $240.20   $240.20  
  7 purchase totals = $1,119.61       $1,200.8562   $1,200.85   $1,200.80   $1,200.90