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 $87.60   9.722%   $96.1165   $96.12   $96.10   $96.10  
  Purchase #2 $229.43   6.436%   $244.1961   $244.20   $244.20   $244.20  
  Purchase #3 $221.34   4.723%   $231.7939   $231.79   $231.80   $231.80  
  Purchase #4 $166.29   3.209%   $171.6262   $171.63   $171.65   $171.60  
  Purchase #5 $222.62   12.537%   $250.5299   $250.53   $250.55   $250.50  
  Purchase #6 $29.93   5.859%   $31.6836   $31.68   $31.70   $31.70  
  Purchase #7 $137.68   9.159%   $150.2901   $150.29   $150.30   $150.30  
  7 purchase totals = $1,094.89       $1,176.2363   $1,176.24   $1,176.30   $1,176.20