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 $43.68   7.728%   $47.0556   $47.06   $47.05   $47.10  
  Purchase #2 $232.67   4.785%   $243.8033   $243.80   $243.80   $243.80  
  Purchase #3 $24.99   6.487%   $26.6111   $26.61   $26.60   $26.60  
  Purchase #4 $148.33   4.863%   $155.5433   $155.54   $155.55   $155.50  
  Purchase #5 $178.43   11.543%   $199.0262   $199.03   $199.05   $199.00  
  Purchase #6 $89.49   11.145%   $99.4637   $99.46   $99.45   $99.50  
  Purchase #7 $190.43   7.740%   $205.1693   $205.17   $205.15   $205.20  
  7 purchase totals = $908.02       $976.6725   $976.67   $976.65   $976.70