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	$133.95	5.467%	$141.273	$141.27	$141.25	$141.30
Purchase #2	$39.77	6.168%	$42.223	$42.22	$42.20	$42.20
Purchase #3	$14.26	13.832%	$16.2324	$16.23	$16.25	$16.20
Purchase #4	$79.57	12.120%	$89.2139	$89.21	$89.20	$89.20
Purchase #5	$50.33	3.426%	$52.0543	$52.05	$52.05	$52.10
Purchase #6	$94.70	11.523%	$105.6123	$105.61	$105.60	$105.60
Purchase #7	$124.91	4.422%	$130.4335	$130.43	$130.45	$130.40
7 purchase totals =	$537.49		$577.0424	$577.02	$577.00	$577.00