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	$104.55	11.839%	$116.9277	$116.93	$116.95	$116.90
Purchase #2	$69.61	12.281%	$78.1588	$78.16	$78.15	$78.20
Purchase #3	$194.29	7.851%	$209.5437	$209.54	$209.55	$209.50
Purchase #4	$83.92	10.595%	$92.8113	$92.81	$92.80	$92.80
Purchase #5	$111.99	13.795%	$127.439	$127.44	$127.45	$127.40
Purchase #6	$241.56	10.459%	$266.8248	$266.82	$266.80	$266.80
Purchase #7	$220.95	4.408%	$230.6895	$230.69	$230.70	$230.70
7 purchase totals =	$1,026.87		$1,122.3948	$1,122.39	$1,122.40	$1,122.30