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 $114.62   11.350%   $127.6294   $127.63   $127.65   $127.60  
  Purchase #2 $153.44   9.114%   $167.4245   $167.42   $167.40   $167.40  
  Purchase #3 $205.71   13.171%   $232.8041   $232.80   $232.80   $232.80  
  Purchase #4 $245.79   7.717%   $264.7576   $264.76   $264.75   $264.80  
  Purchase #5 $199.92   3.348%   $206.6133   $206.61   $206.60   $206.60  
  Purchase #6 $169.99   5.364%   $179.1083   $179.11   $179.10   $179.10  
  Purchase #7 $7.86   6.135%   $8.3422   $8.34   $8.35   $8.30  
  7 purchase totals = $1,097.33       $1,186.6794   $1,186.67   $1,186.65   $1,186.60