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 $61.74   12.688%   $69.5736   $69.57   $69.55   $69.60  
  Purchase #2 $196.69   9.548%   $215.47   $215.47   $215.45   $215.50  
  Purchase #3 $212.26   10.203%   $233.9169   $233.92   $233.90   $233.90  
  Purchase #4 $247.64   4.839%   $259.6233   $259.62   $259.60   $259.60  
  Purchase #5 $216.27   11.659%   $241.4849   $241.48   $241.50   $241.50  
  Purchase #6 $236.43   13.325%   $267.9343   $267.93   $267.95   $267.90  
  Purchase #7 $174.30   6.624%   $185.8456   $185.85   $185.85   $185.80  
  7 purchase totals = $1,345.33       $1,473.8486   $1,473.84   $1,473.80   $1,473.80