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	$145.86	13.338%	$165.3148	$165.31	$165.30	$165.30
Purchase #2	$159.58	5.103%	$167.7234	$167.72	$167.70	$167.70
Purchase #3	$219.86	11.152%	$244.3788	$244.38	$244.40	$244.40
Purchase #4	$14.43	10.321%	$15.9193	$15.92	$15.90	$15.90
Purchase #5	$152.36	8.820%	$165.7982	$165.80	$165.80	$165.80
Purchase #6	$247.96	5.688%	$262.064	$262.06	$262.05	$262.10
Purchase #7	$99.36	7.458%	$106.7703	$106.77	$106.75	$106.80
7 purchase totals =	$1,039.41		$1,127.9688	$1,127.96	$1,127.90	$1,128.00