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 $34.84   5.663%   $36.813   $36.81   $36.80   $36.80  
  Purchase #2 $200.64   13.485%   $227.6963   $227.70   $227.70   $227.70  
  Purchase #3 $187.37   4.397%   $195.6087   $195.61   $195.60   $195.60  
  Purchase #4 $151.80   13.541%   $172.3552   $172.36   $172.35   $172.40  
  Purchase #5 $239.71   12.273%   $269.1296   $269.13   $269.15   $269.10  
  Purchase #6 $56.47   13.471%   $64.0771   $64.08   $64.10   $64.10  
  Purchase #7 $121.50   7.542%   $130.6635   $130.66   $130.65   $130.70  
  7 purchase totals = $992.33       $1,096.3434   $1,096.35   $1,096.35   $1,096.40