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	$138.45	6.496%	$147.4437	$147.44	$147.45	$147.40
Purchase #2	$95.64	10.463%	$105.6468	$105.65	$105.65	$105.60
Purchase #3	$161.74	7.154%	$173.3109	$173.31	$173.30	$173.30
Purchase #4	$108.41	5.456%	$114.3248	$114.32	$114.30	$114.30
Purchase #5	$150.45	3.327%	$155.4555	$155.46	$155.45	$155.50
Purchase #6	$199.29	12.402%	$224.0059	$224.01	$224.00	$224.00
Purchase #7	$84.67	4.116%	$88.155	$88.16	$88.15	$88.20
7 purchase totals =	$938.65		$1,008.3426	$1,008.35	$1,008.30	$1,008.30