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	$72.69	3.279%	$75.0735	$75.07	$75.05	$75.10
Purchase #2	$11.77	5.175%	$12.3791	$12.38	$12.40	$12.40
Purchase #3	$244.80	12.462%	$275.307	$275.31	$275.30	$275.30
Purchase #4	$136.63	4.841%	$143.2443	$143.24	$143.25	$143.20
Purchase #5	$40.42	13.596%	$45.9155	$45.92	$45.90	$45.90
Purchase #6	$53.90	6.452%	$57.3776	$57.38	$57.40	$57.40
Purchase #7	$212.47	9.726%	$233.1348	$233.13	$233.15	$233.10
7 purchase totals =	$772.68		$842.4318	$842.43	$842.45	$842.40