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	$229.71	6.475%	$244.5837	$244.58	$244.60	$244.60
Purchase #2	$69.25	6.288%	$73.6044	$73.60	$73.60	$73.60
Purchase #3	$64.66	11.767%	$72.2685	$72.27	$72.25	$72.30
Purchase #4	$32.56	12.429%	$36.6069	$36.61	$36.60	$36.60
Purchase #5	$45.47	13.603%	$51.6553	$51.66	$51.65	$51.70
Purchase #6	$202.45	13.830%	$230.4488	$230.45	$230.45	$230.40
Purchase #7	$74.40	10.395%	$82.1339	$82.13	$82.15	$82.10
7 purchase totals =	$718.50		$791.3015	$791.30	$791.30	$791.30