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	$130.62	8.245%	$141.3896	$141.39	$141.40	$141.40
Purchase #2	$26.95	4.800%	$28.2436	$28.24	$28.25	$28.20
Purchase #3	$12.37	9.687%	$13.5683	$13.57	$13.55	$13.60
Purchase #4	$185.63	6.814%	$198.2788	$198.28	$198.30	$198.30
Purchase #5	$70.39	10.814%	$78.002	$78.00	$78.00	$78.00
Purchase #6	$246.39	4.175%	$256.6768	$256.68	$256.70	$256.70
Purchase #7	$122.86	3.704%	$127.4107	$127.41	$127.40	$127.40
7 purchase totals =	$795.21		$843.5698	$843.57	$843.60	$843.60