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	$55.45	9.549%	$60.7449	$60.74	$60.75	$60.70
Purchase #2	$171.41	13.465%	$194.4904	$194.49	$194.50	$194.50
Purchase #3	$12.64	7.367%	$13.5712	$13.57	$13.55	$13.60
Purchase #4	$179.68	9.325%	$196.4352	$196.44	$196.45	$196.40
Purchase #5	$193.85	10.848%	$214.8788	$214.88	$214.90	$214.90
Purchase #6	$88.71	13.333%	$100.5377	$100.54	$100.55	$100.50
Purchase #7	$225.32	6.803%	$240.6485	$240.65	$240.65	$240.60
7 purchase totals =	$927.06		$1,021.3067	$1,021.31	$1,021.35	$1,021.20