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	$44.36	4.585%	$46.3939	$46.39	$46.40	$46.40
Purchase #2	$231.87	9.720%	$254.4078	$254.41	$254.40	$254.40
Purchase #3	$159.61	13.539%	$181.2196	$181.22	$181.20	$181.20
Purchase #4	$65.83	8.666%	$71.5348	$71.53	$71.55	$71.50
Purchase #5	$92.82	7.186%	$99.49	$99.49	$99.50	$99.50
Purchase #6	$17.45	12.240%	$19.5859	$19.59	$19.60	$19.60
Purchase #7	$35.89	13.285%	$40.658	$40.66	$40.65	$40.70
7 purchase totals =	$647.83		$713.2900	$713.29	$713.30	$713.30