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 $61.45   11.615%   $68.5874   $68.59   $68.60   $68.60  
  Purchase #2 $68.47   7.208%   $73.4053   $73.41   $73.40   $73.40  
  Purchase #3 $55.69   8.160%   $60.2343   $60.23   $60.25   $60.20  
  Purchase #4 $243.91   6.309%   $259.2983   $259.30   $259.30   $259.30  
  Purchase #5 $169.78   7.286%   $182.1502   $182.15   $182.15   $182.20  
  Purchase #6 $200.86   11.310%   $223.5773   $223.58   $223.60   $223.60  
  Purchase #7 $210.25   4.599%   $219.9194   $219.92   $219.90   $219.90  
  7 purchase totals = $1,010.41       $1,087.1722   $1,087.18   $1,087.20   $1,087.20