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 $98.39   9.717%   $107.9506   $107.95   $107.95   $108.00  
  Purchase #2 $183.29   7.456%   $196.9561   $196.96   $196.95   $197.00  
  Purchase #3 $6.54   6.311%   $6.9527   $6.95   $6.95   $7.00  
  Purchase #4 $176.42   11.269%   $196.3008   $196.30   $196.30   $196.30  
  Purchase #5 $206.57   3.655%   $214.1201   $214.12   $214.10   $214.10  
  Purchase #6 $211.59   11.735%   $236.4201   $236.42   $236.40   $236.40  
  Purchase #7 $89.39   5.203%   $94.041   $94.04   $94.05   $94.00  
  7 purchase totals = $972.19       $1,052.7414   $1,052.74   $1,052.70   $1,052.80