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 $119.93   9.804%   $131.6879   $131.69   $131.70   $131.70  
  Purchase #2 $70.57   7.184%   $75.6397   $75.64   $75.65   $75.60  
  Purchase #3 $165.96   7.106%   $177.7531   $177.75   $177.75   $177.80  
  Purchase #4 $178.59   3.541%   $184.9139   $184.91   $184.90   $184.90  
  Purchase #5 $239.84   9.636%   $262.951   $262.95   $262.95   $263.00  
  Purchase #6 $147.47   3.748%   $152.9972   $153.00   $153.00   $153.00  
  Purchase #7 $199.41   5.252%   $209.883   $209.88   $209.90   $209.90  
  7 purchase totals = $1,121.77       $1,195.8258   $1,195.82   $1,195.85   $1,195.90