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	$41.83	7.313%	$44.889	$44.89	$44.90	$44.90
Purchase #2	$159.43	5.344%	$167.9499	$167.95	$167.95	$167.90
Purchase #3	$134.92	10.783%	$149.4684	$149.47	$149.45	$149.50
Purchase #4	$229.71	12.569%	$258.5822	$258.58	$258.60	$258.60
Purchase #5	$92.96	8.170%	$100.5548	$100.55	$100.55	$100.60
Purchase #6	$104.49	9.622%	$114.544	$114.54	$114.55	$114.50
Purchase #7	$67.62	7.588%	$72.751	$72.75	$72.75	$72.80
7 purchase totals =	$830.96		$908.7393	$908.73	$908.75	$908.80