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 $184.28   5.293%   $194.0339   $194.03   $194.05   $194.00  
  Purchase #2 $90.99   13.403%   $103.1854   $103.19   $103.20   $103.20  
  Purchase #3 $15.51   12.351%   $17.4256   $17.43   $17.45   $17.40  
  Purchase #4 $210.80   5.802%   $223.0306   $223.03   $223.05   $223.00  
  Purchase #5 $165.89   4.741%   $173.7548   $173.75   $173.75   $173.80  
  Purchase #6 $172.80   3.118%   $178.1879   $178.19   $178.20   $178.20  
  Purchase #7 $170.34   13.188%   $192.8044   $192.80   $192.80   $192.80  
  7 purchase totals = $1,010.61       $1,082.4226   $1,082.42   $1,082.50   $1,082.40