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	$195.91	13.124%	$221.6212	$221.62	$221.60	$221.60
Purchase #2	$111.44	12.420%	$125.2808	$125.28	$125.30	$125.30
Purchase #3	$19.74	3.768%	$20.4838	$20.48	$20.50	$20.50
Purchase #4	$227.49	12.206%	$255.2574	$255.26	$255.25	$255.30
Purchase #5	$81.55	11.145%	$90.6387	$90.64	$90.65	$90.60
Purchase #6	$223.35	7.319%	$239.697	$239.70	$239.70	$239.70
Purchase #7	$158.69	13.361%	$179.8926	$179.89	$179.90	$179.90
7 purchase totals =	$1,018.17		$1,132.8715	$1,132.87	$1,132.90	$1,132.90