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	$75.26	10.424%	$83.1051	$83.11	$83.10	$83.10
Purchase #2	$97.62	3.116%	$100.6618	$100.66	$100.65	$100.70
Purchase #3	$172.52	9.509%	$188.9249	$188.92	$188.90	$188.90
Purchase #4	$55.83	9.342%	$61.0456	$61.05	$61.05	$61.00
Purchase #5	$33.54	4.561%	$35.0698	$35.07	$35.05	$35.10
Purchase #6	$185.94	13.864%	$211.7187	$211.72	$211.70	$211.70
Purchase #7	$46.96	5.283%	$49.4409	$49.44	$49.45	$49.40
7 purchase totals =	$667.67		$729.9668	$729.97	$729.90	$729.90