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	$191.34	4.722%	$200.3751	$200.38	$200.40	$200.40
Purchase #2	$91.53	7.472%	$98.3691	$98.37	$98.35	$98.40
Purchase #3	$129.83	3.253%	$134.0534	$134.05	$134.05	$134.10
Purchase #4	$158.65	6.103%	$168.3324	$168.33	$168.35	$168.30
Purchase #5	$211.85	5.246%	$222.9637	$222.96	$222.95	$223.00
Purchase #6	$226.85	6.779%	$242.2282	$242.23	$242.25	$242.20
Purchase #7	$10.26	4.690%	$10.7412	$10.74	$10.75	$10.70
7 purchase totals =	$1,020.31		$1,077.0631	$1,077.06	$1,077.10	$1,077.10