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 $84.49   12.398%   $94.9651   $94.97   $94.95   $95.00  
  Purchase #2 $24.51   11.576%   $27.3473   $27.35   $27.35   $27.30  
  Purchase #3 $230.93   7.449%   $248.132   $248.13   $248.15   $248.10  
  Purchase #4 $189.70   3.754%   $196.8213   $196.82   $196.80   $196.80  
  Purchase #5 $140.26   8.427%   $152.0797   $152.08   $152.10   $152.10  
  Purchase #6 $89.91   9.269%   $98.2438   $98.24   $98.25   $98.20  
  Purchase #7 $125.65   3.867%   $130.5089   $130.51   $130.50   $130.50  
  7 purchase totals = $885.45       $948.0981   $948.10   $948.10   $948.00