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	$112.56	13.466%	$127.7173	$127.72	$127.70	$127.70
Purchase #2	$55.47	11.773%	$62.0005	$62.00	$62.00	$62.00
Purchase #3	$113.91	3.684%	$118.1064	$118.11	$118.10	$118.10
Purchase #4	$79.39	12.445%	$89.2701	$89.27	$89.25	$89.30
Purchase #5	$191.26	8.260%	$207.0581	$207.06	$207.05	$207.10
Purchase #6	$151.89	8.501%	$164.8022	$164.80	$164.80	$164.80
Purchase #7	$95.33	6.434%	$101.4635	$101.46	$101.45	$101.50
7 purchase totals =	$799.81		$870.4181	$870.42	$870.35	$870.50