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	$231.61	4.468%	$241.9583	$241.96	$241.95	$242.00
Purchase #2	$205.85	8.224%	$222.7791	$222.78	$222.80	$222.80
Purchase #3	$36.88	9.621%	$40.4282	$40.43	$40.45	$40.40
Purchase #4	$57.67	6.506%	$61.422	$61.42	$61.40	$61.40
Purchase #5	$134.65	10.867%	$149.2824	$149.28	$149.30	$149.30
Purchase #6	$114.72	5.159%	$120.6384	$120.64	$120.65	$120.60
Purchase #7	$221.95	5.761%	$234.7365	$234.74	$234.75	$234.70
7 purchase totals =	$1,003.33		$1,071.2449	$1,071.25	$1,071.30	$1,071.20