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 $86.69   11.255%   $96.447   $96.45   $96.45   $96.40  
  Purchase #2 $199.27   12.343%   $223.8659   $223.87   $223.85   $223.90  
  Purchase #3 $58.59   7.729%   $63.1184   $63.12   $63.10   $63.10  
  Purchase #4 $158.81   10.563%   $175.5851   $175.59   $175.60   $175.60  
  Purchase #5 $217.75   9.531%   $238.5038   $238.50   $238.50   $238.50  
  Purchase #6 $116.71   7.631%   $125.6161   $125.62   $125.60   $125.60  
  Purchase #7 $142.73   3.131%   $147.1989   $147.20   $147.20   $147.20  
  7 purchase totals = $980.55       $1,070.3352   $1,070.35   $1,070.30   $1,070.30