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 $194.82   5.583%   $205.6968   $205.70   $205.70   $205.70  
  Purchase #2 $25.91   12.434%   $29.1316   $29.13   $29.15   $29.10  
  Purchase #3 $130.74   3.323%   $135.0845   $135.08   $135.10   $135.10  
  Purchase #4 $249.81   5.484%   $263.5096   $263.51   $263.50   $263.50  
  Purchase #5 $40.68   11.687%   $45.4343   $45.43   $45.45   $45.40  
  Purchase #6 $211.50   3.787%   $219.5095   $219.51   $219.50   $219.50  
  Purchase #7 $57.55   13.828%   $65.508   $65.51   $65.50   $65.50  
  7 purchase totals = $911.01       $963.8743   $963.87   $963.90   $963.80