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	$119.95	12.431%	$134.861	$134.86	$134.85	$134.90
Purchase #2	$247.29	12.220%	$277.5088	$277.51	$277.50	$277.50
Purchase #3	$170.79	6.422%	$181.7581	$181.76	$181.75	$181.80
Purchase #4	$58.78	5.852%	$62.2198	$62.22	$62.20	$62.20
Purchase #5	$245.89	6.594%	$262.104	$262.10	$262.10	$262.10
Purchase #6	$53.93	5.518%	$56.9059	$56.91	$56.90	$56.90
Purchase #7	$75.91	13.198%	$85.9286	$85.93	$85.95	$85.90
7 purchase totals =	$972.54		$1,061.2862	$1,061.29	$1,061.25	$1,061.30