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 $84.97   12.834%   $95.875   $95.88   $95.90   $95.90  
  Purchase #2 $159.85   10.507%   $176.6454   $176.65   $176.65   $176.60  
  Purchase #3 $128.92   5.860%   $136.4747   $136.47   $136.45   $136.50  
  Purchase #4 $193.91   12.301%   $217.7629   $217.76   $217.75   $217.80  
  Purchase #5 $211.74   4.244%   $220.7262   $220.73   $220.75   $220.70  
  Purchase #6 $213.51   11.366%   $237.7775   $237.78   $237.80   $237.80  
  Purchase #7 $195.57   12.324%   $219.672   $219.67   $219.65   $219.70  
  7 purchase totals = $1,188.47       $1,304.9337   $1,304.94   $1,304.95   $1,305.00