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	$66.44	8.391%	$72.015	$72.02	$72.00	$72.00
Purchase #2	$159.74	7.152%	$171.1646	$171.16	$171.15	$171.20
Purchase #3	$19.89	11.315%	$22.1406	$22.14	$22.15	$22.10
Purchase #4	$130.58	3.239%	$134.8095	$134.81	$134.80	$134.80
Purchase #5	$242.53	4.839%	$254.266	$254.27	$254.25	$254.30
Purchase #6	$126.54	3.599%	$131.0942	$131.09	$131.10	$131.10
Purchase #7	$191.65	13.771%	$218.0421	$218.04	$218.05	$218.00
7 purchase totals =	$937.37		$1,003.5320	$1,003.53	$1,003.50	$1,003.50