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	$111.63	10.714%	$123.59	$123.59	$123.60	$123.60
Purchase #2	$188.67	8.421%	$204.5579	$204.56	$204.55	$204.60
Purchase #3	$212.65	4.462%	$222.1384	$222.14	$222.15	$222.10
Purchase #4	$36.85	7.160%	$39.4885	$39.49	$39.50	$39.50
Purchase #5	$14.35	4.178%	$14.9495	$14.95	$14.95	$14.90
Purchase #6	$136.72	5.169%	$143.7871	$143.79	$143.80	$143.80
Purchase #7	$244.39	7.684%	$263.1689	$263.17	$263.15	$263.20
7 purchase totals =	$945.26		$1,011.6803	$1,011.69	$1,011.70	$1,011.70