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 $69.95   4.152%   $72.8543   $72.85   $72.85   $72.90  
  Purchase #2 $154.47   13.115%   $174.7287   $174.73   $174.75   $174.70  
  Purchase #3 $177.26   13.569%   $201.3124   $201.31   $201.30   $201.30  
  Purchase #4 $225.28   4.122%   $234.566   $234.57   $234.55   $234.60  
  Purchase #5 $128.27   3.224%   $132.4054   $132.41   $132.40   $132.40  
  Purchase #6 $33.60   7.187%   $36.0148   $36.01   $36.00   $36.00  
  Purchase #7 $178.83   7.837%   $192.8449   $192.84   $192.85   $192.80  
  7 purchase totals = $967.66       $1,044.7265   $1,044.72   $1,044.70   $1,044.70