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 $85.47   12.551%   $96.1973   $96.20   $96.20   $96.20  
  Purchase #2 $129.78   3.590%   $134.4391   $134.44   $134.45   $134.40  
  Purchase #3 $127.43   4.608%   $133.302   $133.30   $133.30   $133.30  
  Purchase #4 $240.40   12.461%   $270.3562   $270.36   $270.35   $270.40  
  Purchase #5 $131.63   10.795%   $145.8395   $145.84   $145.85   $145.80  
  Purchase #6 $87.49   4.757%   $91.6519   $91.65   $91.65   $91.70  
  Purchase #7 $220.46   4.599%   $230.599   $230.60   $230.60   $230.60  
  7 purchase totals = $1,022.66       $1,102.3850   $1,102.39   $1,102.40   $1,102.40