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	$99.59	6.607%	$106.1699	$106.17	$106.15	$106.20
Purchase #2	$10.90	12.369%	$12.2482	$12.25	$12.25	$12.20
Purchase #3	$231.86	5.664%	$244.9926	$244.99	$245.00	$245.00
Purchase #4	$165.51	5.507%	$174.6246	$174.62	$174.60	$174.60
Purchase #5	$170.72	11.635%	$190.5833	$190.58	$190.60	$190.60
Purchase #6	$223.31	13.560%	$253.5908	$253.59	$253.60	$253.60
Purchase #7	$234.86	10.659%	$259.8937	$259.89	$259.90	$259.90
7 purchase totals =	$1,136.75		$1,242.1031	$1,242.09	$1,242.10	$1,242.10