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	$84.92	7.846%	$91.5828	$91.58	$91.60	$91.60
Purchase #2	$219.78	9.792%	$241.3009	$241.30	$241.30	$241.30
Purchase #3	$170.95	4.404%	$178.4786	$178.48	$178.50	$178.50
Purchase #4	$57.35	5.475%	$60.4899	$60.49	$60.50	$60.50
Purchase #5	$148.95	13.660%	$169.2966	$169.30	$169.30	$169.30
Purchase #6	$189.57	8.408%	$205.509	$205.51	$205.50	$205.50
Purchase #7	$122.87	7.111%	$131.6073	$131.61	$131.60	$131.60
7 purchase totals =	$994.39		$1,078.2651	$1,078.27	$1,078.30	$1,078.30