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	$146.74	13.745%	$166.9094	$166.91	$166.90	$166.90
Purchase #2	$144.75	11.165%	$160.9113	$160.91	$160.90	$160.90
Purchase #3	$223.60	11.641%	$249.6293	$249.63	$249.65	$249.60
Purchase #4	$78.60	4.539%	$82.1677	$82.17	$82.15	$82.20
Purchase #5	$48.64	10.539%	$53.7662	$53.77	$53.75	$53.80
Purchase #6	$158.39	4.769%	$165.9436	$165.94	$165.95	$165.90
Purchase #7	$248.91	6.711%	$265.6144	$265.61	$265.60	$265.60
7 purchase totals =	$1,049.63		$1,144.9419	$1,144.94	$1,144.90	$1,144.90