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 $233.77   5.637%   $246.9476   $246.95   $246.95   $246.90  
  Purchase #2 $198.95   13.396%   $225.6013   $225.60   $225.60   $225.60  
  Purchase #3 $207.30   12.539%   $233.2933   $233.29   $233.30   $233.30  
  Purchase #4 $23.77   6.423%   $25.2967   $25.30   $25.30   $25.30  
  Purchase #5 $230.48   9.103%   $251.4606   $251.46   $251.45   $251.50  
  Purchase #6 $192.59   12.197%   $216.0802   $216.08   $216.10   $216.10  
  Purchase #7 $157.60   7.835%   $169.948   $169.95   $169.95   $169.90  
  7 purchase totals = $1,244.46       $1,368.6277   $1,368.63   $1,368.65   $1,368.60