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	$144.68	12.608%	$162.9213	$162.92	$162.90	$162.90
Purchase #2	$184.25	13.640%	$209.3817	$209.38	$209.40	$209.40
Purchase #3	$239.75	4.368%	$250.2223	$250.22	$250.20	$250.20
Purchase #4	$56.40	8.350%	$61.1094	$61.11	$61.10	$61.10
Purchase #5	$131.30	13.433%	$148.9375	$148.94	$148.95	$148.90
Purchase #6	$171.94	10.754%	$190.4304	$190.43	$190.45	$190.40
Purchase #7	$10.45	8.525%	$11.3409	$11.34	$11.35	$11.30
7 purchase totals =	$938.77		$1,034.3435	$1,034.34	$1,034.35	$1,034.20