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	$49.31	9.604%	$54.0457	$54.05	$54.05	$54.00
Purchase #2	$106.43	4.864%	$111.6068	$111.61	$111.60	$111.60
Purchase #3	$172.79	3.196%	$178.3124	$178.31	$178.30	$178.30
Purchase #4	$239.44	3.695%	$248.2873	$248.29	$248.30	$248.30
Purchase #5	$62.65	6.339%	$66.6214	$66.62	$66.60	$66.60
Purchase #6	$84.43	4.828%	$88.5063	$88.51	$88.50	$88.50
Purchase #7	$52.91	12.519%	$59.5338	$59.53	$59.55	$59.50
7 purchase totals =	$767.96		$806.9137	$806.92	$806.90	$806.80