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 $210.44   11.169%   $233.944   $233.94   $233.95   $233.90  
  Purchase #2 $148.65   6.511%   $158.3286   $158.33   $158.35   $158.30  
  Purchase #3 $114.98   7.626%   $123.7484   $123.75   $123.75   $123.70  
  Purchase #4 $85.48   7.295%   $91.7158   $91.72   $91.70   $91.70  
  Purchase #5 $213.38   10.618%   $236.0367   $236.04   $236.05   $236.00  
  Purchase #6 $122.54   12.854%   $138.2913   $138.29   $138.30   $138.30  
  Purchase #7 $116.77   7.243%   $125.2277   $125.23   $125.25   $125.20  
  7 purchase totals = $1,012.24       $1,107.2925   $1,107.30   $1,107.35   $1,107.10