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 $60.97   10.119%   $67.1396   $67.14   $67.15   $67.10  
  Purchase #2 $184.98   8.294%   $200.3222   $200.32   $200.30   $200.30  
  Purchase #3 $109.91   10.362%   $121.2989   $121.30   $121.30   $121.30  
  Purchase #4 $233.90   5.321%   $246.3458   $246.35   $246.35   $246.30  
  Purchase #5 $237.93   10.498%   $262.9079   $262.91   $262.90   $262.90  
  Purchase #6 $88.35   6.414%   $94.0168   $94.02   $94.00   $94.00  
  Purchase #7 $180.83   12.175%   $202.8461   $202.85   $202.85   $202.80  
  7 purchase totals = $1,096.87       $1,194.8773   $1,194.89   $1,194.85   $1,194.70