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 $160.51   5.692%   $169.6462   $169.65   $169.65   $169.60  
  Purchase #2 $41.39   11.732%   $46.2459   $46.25   $46.25   $46.20  
  Purchase #3 $232.61   9.326%   $254.3032   $254.30   $254.30   $254.30  
  Purchase #4 $110.55   8.371%   $119.8041   $119.80   $119.80   $119.80  
  Purchase #5 $53.60   5.339%   $56.4617   $56.46   $56.45   $56.50  
  Purchase #6 $55.60   8.523%   $60.3388   $60.34   $60.35   $60.30  
  Purchase #7 $220.98   5.603%   $233.3615   $233.36   $233.35   $233.40  
  7 purchase totals = $875.24       $940.1614   $940.16   $940.15   $940.10