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 $112.63   11.820%   $125.9429   $125.94   $125.95   $125.90  
  Purchase #2 $49.68   9.581%   $54.4398   $54.44   $54.45   $54.40  
  Purchase #3 $240.74   11.111%   $267.4886   $267.49   $267.50   $267.50  
  Purchase #4 $166.49   6.254%   $176.9023   $176.90   $176.90   $176.90  
  Purchase #5 $224.47   8.368%   $243.2536   $243.25   $243.25   $243.30  
  Purchase #6 $196.47   11.405%   $218.8774   $218.88   $218.90   $218.90  
  Purchase #7 $92.49   4.173%   $96.3496   $96.35   $96.35   $96.30  
  7 purchase totals = $1,082.97       $1,183.2542   $1,183.25   $1,183.30   $1,183.20