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	$55.31	12.479%	$62.2121	$62.21	$62.20	$62.20
Purchase #2	$98.64	12.717%	$111.184	$111.18	$111.20	$111.20
Purchase #3	$112.32	5.623%	$118.6358	$118.64	$118.65	$118.60
Purchase #4	$40.98	11.748%	$45.7943	$45.79	$45.80	$45.80
Purchase #5	$125.93	13.205%	$142.5591	$142.56	$142.55	$142.60
Purchase #6	$174.46	12.512%	$196.2884	$196.29	$196.30	$196.30
Purchase #7	$10.97	4.204%	$11.4312	$11.43	$11.45	$11.40
7 purchase totals =	$618.61		$688.1049	$688.10	$688.15	$688.10