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 $68.37   10.672%   $75.6664   $75.67   $75.65   $75.70  
  Purchase #2 $217.67   3.637%   $225.5867   $225.59   $225.60   $225.60  
  Purchase #3 $105.99   9.496%   $116.0548   $116.05   $116.05   $116.10  
  Purchase #4 $185.60   11.179%   $206.3482   $206.35   $206.35   $206.30  
  Purchase #5 $213.42   11.668%   $238.3218   $238.32   $238.30   $238.30  
  Purchase #6 $205.57   13.269%   $232.8471   $232.85   $232.85   $232.80  
  Purchase #7 $211.68   9.635%   $232.0754   $232.08   $232.10   $232.10  
  7 purchase totals = $1,208.30       $1,326.9004   $1,326.91   $1,326.90   $1,326.90