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	$126.33	5.485%	$133.2592	$133.26	$133.25	$133.30
Purchase #2	$248.28	7.317%	$266.4466	$266.45	$266.45	$266.40
Purchase #3	$66.51	8.864%	$72.4054	$72.41	$72.40	$72.40
Purchase #4	$65.27	10.178%	$71.9132	$71.91	$71.90	$71.90
Purchase #5	$106.55	9.503%	$116.6754	$116.68	$116.70	$116.70
Purchase #6	$130.65	10.764%	$144.7132	$144.71	$144.70	$144.70
Purchase #7	$93.97	6.275%	$99.8666	$99.87	$99.85	$99.90
7 purchase totals =	$837.56		$905.2796	$905.29	$905.25	$905.30