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	$202.52	13.648%	$230.1599	$230.16	$230.15	$230.20
Purchase #2	$209.68	6.409%	$223.1184	$223.12	$223.10	$223.10
Purchase #3	$64.84	11.720%	$72.4392	$72.44	$72.45	$72.40
Purchase #4	$38.54	4.303%	$40.1984	$40.20	$40.20	$40.20
Purchase #5	$48.27	10.359%	$53.2703	$53.27	$53.25	$53.30
Purchase #6	$85.27	5.264%	$89.7586	$89.76	$89.75	$89.80
Purchase #7	$215.96	13.177%	$244.417	$244.42	$244.40	$244.40
7 purchase totals =	$865.08		$953.3618	$953.37	$953.30	$953.40