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 $61.49   10.607%   $68.0122   $68.01   $68.00   $68.00  
  Purchase #2 $216.76   12.813%   $244.5335   $244.53   $244.55   $244.50  
  Purchase #3 $240.81   6.431%   $256.2965   $256.30   $256.30   $256.30  
  Purchase #4 $179.32   9.849%   $196.9812   $196.98   $197.00   $197.00  
  Purchase #5 $60.74   11.554%   $67.7579   $67.76   $67.75   $67.80  
  Purchase #6 $119.54   8.872%   $130.1456   $130.15   $130.15   $130.10  
  Purchase #7 $204.59   5.415%   $215.6685   $215.67   $215.65   $215.70  
  7 purchase totals = $1,083.25       $1,179.3954   $1,179.40   $1,179.40   $1,179.40