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 $118.69   5.343%   $125.0316   $125.03   $125.05   $125.00  
  Purchase #2 $244.74   3.463%   $253.2153   $253.22   $253.20   $253.20  
  Purchase #3 $65.56   11.404%   $73.0365   $73.04   $73.05   $73.00  
  Purchase #4 $97.38   11.260%   $108.345   $108.35   $108.35   $108.30  
  Purchase #5 $188.59   12.249%   $211.6904   $211.69   $211.70   $211.70  
  Purchase #6 $89.78   6.415%   $95.5394   $95.54   $95.55   $95.50  
  Purchase #7 $162.71   10.325%   $179.5098   $179.51   $179.50   $179.50  
  7 purchase totals = $967.45       $1,046.3680   $1,046.38   $1,046.40   $1,046.20