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	$241.66	8.214%	$261.51	$261.51	$261.50	$261.50
Purchase #2	$230.38	4.601%	$240.9798	$240.98	$241.00	$241.00
Purchase #3	$185.70	5.837%	$196.5393	$196.54	$196.55	$196.50
Purchase #4	$169.65	6.627%	$180.8927	$180.89	$180.90	$180.90
Purchase #5	$75.81	6.598%	$80.8119	$80.81	$80.80	$80.80
Purchase #6	$85.37	5.709%	$90.2438	$90.24	$90.25	$90.20
Purchase #7	$141.25	7.520%	$151.872	$151.87	$151.85	$151.90
7 purchase totals =	$1,129.82		$1,202.8495	$1,202.84	$1,202.85	$1,202.80