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	$40.60	13.567%	$46.1082	$46.11	$46.10	$46.10
Purchase #2	$179.28	9.346%	$196.0355	$196.04	$196.05	$196.00
Purchase #3	$82.86	10.786%	$91.7973	$91.80	$91.80	$91.80
Purchase #4	$34.31	11.720%	$38.3311	$38.33	$38.35	$38.30
Purchase #5	$17.77	4.252%	$18.5256	$18.53	$18.55	$18.50
Purchase #6	$144.86	4.468%	$151.3323	$151.33	$151.35	$151.30
Purchase #7	$185.33	11.763%	$207.1304	$207.13	$207.15	$207.10
7 purchase totals =	$685.01		$749.2604	$749.27	$749.35	$749.10