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	$135.80	6.378%	$144.4613	$144.46	$144.45	$144.50
Purchase #2	$50.55	5.335%	$53.2468	$53.25	$53.25	$53.20
Purchase #3	$229.87	11.622%	$256.5855	$256.59	$256.60	$256.60
Purchase #4	$243.84	3.312%	$251.916	$251.92	$251.90	$251.90
Purchase #5	$23.62	12.541%	$26.5822	$26.58	$26.60	$26.60
Purchase #6	$232.76	9.575%	$255.0468	$255.05	$255.05	$255.00
Purchase #7	$156.85	3.758%	$162.7444	$162.74	$162.75	$162.70
7 purchase totals =	$1,073.29		$1,150.5830	$1,150.59	$1,150.60	$1,150.50