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 $182.59   6.408%   $194.2904   $194.29   $194.30   $194.30  
  Purchase #2 $239.90   10.343%   $264.7129   $264.71   $264.70   $264.70  
  Purchase #3 $134.88   9.519%   $147.7192   $147.72   $147.70   $147.70  
  Purchase #4 $49.74   10.431%   $54.9284   $54.93   $54.95   $54.90  
  Purchase #5 $68.95   10.603%   $76.2608   $76.26   $76.25   $76.30  
  Purchase #6 $233.59   3.291%   $241.2774   $241.28   $241.30   $241.30  
  Purchase #7 $126.34   6.803%   $134.9349   $134.93   $134.95   $134.90  
  7 purchase totals = $1,035.99       $1,114.1240   $1,114.12   $1,114.15   $1,114.10