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 $44.46   8.241%   $48.1239   $48.12   $48.10   $48.10  
  Purchase #2 $193.87   4.864%   $203.2998   $203.30   $203.30   $203.30  
  Purchase #3 $209.53   11.154%   $232.901   $232.90   $232.90   $232.90  
  Purchase #4 $227.86   9.561%   $249.6457   $249.65   $249.65   $249.60  
  Purchase #5 $99.65   13.559%   $113.1615   $113.16   $113.15   $113.20  
  Purchase #6 $173.34   13.141%   $196.1186   $196.12   $196.10   $196.10  
  Purchase #7 $132.90   13.305%   $150.5823   $150.58   $150.60   $150.60  
  7 purchase totals = $1,081.61       $1,193.8328   $1,193.83   $1,193.80   $1,193.80