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	$152.91	3.866%	$158.8215	$158.82	$158.80	$158.80
Purchase #2	$104.37	6.495%	$111.1488	$111.15	$111.15	$111.10
Purchase #3	$78.32	3.790%	$81.2883	$81.29	$81.30	$81.30
Purchase #4	$178.88	5.163%	$188.1156	$188.12	$188.10	$188.10
Purchase #5	$206.41	13.479%	$234.232	$234.23	$234.25	$234.20
Purchase #6	$167.28	12.860%	$188.7922	$188.79	$188.80	$188.80
Purchase #7	$47.54	5.245%	$50.0335	$50.03	$50.05	$50.00
7 purchase totals =	$935.71		$1,012.4319	$1,012.43	$1,012.45	$1,012.30