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 $176.29   3.493%   $182.4478   $182.45   $182.45   $182.40  
  Purchase #2 $87.61   11.455%   $97.6457   $97.65   $97.65   $97.60  
  Purchase #3 $85.84   10.427%   $94.7905   $94.79   $94.80   $94.80  
  Purchase #4 $26.29   12.752%   $29.6425   $29.64   $29.65   $29.60  
  Purchase #5 $211.40   3.644%   $219.1034   $219.10   $219.10   $219.10  
  Purchase #6 $156.44   6.502%   $166.6117   $166.61   $166.60   $166.60  
  Purchase #7 $244.92   5.774%   $259.0617   $259.06   $259.05   $259.10  
  7 purchase totals = $988.79       $1,049.3033   $1,049.30   $1,049.30   $1,049.20