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 $191.75   5.583%   $202.4554   $202.46   $202.45   $202.50  
  Purchase #2 $7.76   7.191%   $8.318   $8.32   $8.30   $8.30  
  Purchase #3 $197.39   3.621%   $204.5375   $204.54   $204.55   $204.50  
  Purchase #4 $216.48   13.483%   $245.668   $245.67   $245.65   $245.70  
  Purchase #5 $13.68   9.333%   $14.9568   $14.96   $14.95   $15.00  
  Purchase #6 $128.55   5.278%   $135.3349   $135.33   $135.35   $135.30  
  Purchase #7 $213.53   13.293%   $241.9145   $241.91   $241.90   $241.90  
  7 purchase totals = $969.14       $1,053.1851   $1,053.19   $1,053.15   $1,053.20