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	$72.56	8.561%	$78.7719	$78.77	$78.75	$78.80
Purchase #2	$11.65	8.141%	$12.5984	$12.60	$12.60	$12.60
Purchase #3	$57.98	10.717%	$64.1937	$64.19	$64.20	$64.20
Purchase #4	$106.80	11.735%	$119.333	$119.33	$119.35	$119.30
Purchase #5	$75.32	6.745%	$80.4003	$80.40	$80.40	$80.40
Purchase #6	$152.27	4.657%	$159.3612	$159.36	$159.35	$159.40
Purchase #7	$242.66	5.361%	$255.669	$255.67	$255.65	$255.70
7 purchase totals =	$719.24		$770.3275	$770.32	$770.30	$770.40