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	$248.56	6.282%	$264.1745	$264.17	$264.15	$264.20
Purchase #2	$56.89	7.184%	$60.977	$60.98	$61.00	$61.00
Purchase #3	$11.80	8.135%	$12.7599	$12.76	$12.75	$12.80
Purchase #4	$139.45	5.194%	$146.693	$146.69	$146.70	$146.70
Purchase #5	$118.89	3.771%	$123.3733	$123.37	$123.35	$123.40
Purchase #6	$51.99	6.774%	$55.5118	$55.51	$55.50	$55.50
Purchase #7	$139.70	3.136%	$144.081	$144.08	$144.10	$144.10
7 purchase totals =	$767.28		$807.5705	$807.56	$807.55	$807.70