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 $195.53   10.232%   $215.5366   $215.54   $215.55   $215.50  
  Purchase #2 $216.46   4.330%   $225.8327   $225.83   $225.85   $225.80  
  Purchase #3 $44.83   6.463%   $47.7274   $47.73   $47.75   $47.70  
  Purchase #4 $174.78   3.768%   $181.3657   $181.37   $181.35   $181.40  
  Purchase #5 $188.40   4.555%   $196.9816   $196.98   $197.00   $197.00  
  Purchase #6 $165.40   3.792%   $171.672   $171.67   $171.65   $171.70  
  Purchase #7 $216.54   9.589%   $237.304   $237.30   $237.30   $237.30  
  7 purchase totals = $1,201.94       $1,276.4200   $1,276.42   $1,276.45   $1,276.40