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 $162.35   13.804%   $184.7608   $184.76   $184.75   $184.80  
  Purchase #2 $178.54   11.846%   $199.6898   $199.69   $199.70   $199.70  
  Purchase #3 $99.96   8.274%   $108.2307   $108.23   $108.25   $108.20  
  Purchase #4 $183.57   9.434%   $200.888   $200.89   $200.90   $200.90  
  Purchase #5 $91.29   5.540%   $96.3475   $96.35   $96.35   $96.30  
  Purchase #6 $213.82   6.476%   $227.667   $227.67   $227.65   $227.70  
  Purchase #7 $84.60   4.208%   $88.16   $88.16   $88.15   $88.20  
  7 purchase totals = $1,014.13       $1,105.7438   $1,105.75   $1,105.75   $1,105.80