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	$44.37	4.592%	$46.4075	$46.41	$46.40	$46.40
Purchase #2	$167.82	7.216%	$179.9299	$179.93	$179.95	$179.90
Purchase #3	$83.59	5.803%	$88.4407	$88.44	$88.45	$88.40
Purchase #4	$244.72	3.722%	$253.8285	$253.83	$253.85	$253.80
Purchase #5	$221.34	5.777%	$234.1268	$234.13	$234.15	$234.10
Purchase #6	$89.94	13.238%	$101.8463	$101.85	$101.85	$101.80
Purchase #7	$149.53	10.771%	$165.6359	$165.64	$165.65	$165.60
7 purchase totals =	$1,001.31		$1,070.2156	$1,070.23	$1,070.30	$1,070.00