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	$148.56	5.159%	$156.2242	$156.22	$156.20	$156.20
Purchase #2	$18.79	9.748%	$20.6216	$20.62	$20.60	$20.60
Purchase #3	$5.67	11.312%	$6.3114	$6.31	$6.30	$6.30
Purchase #4	$88.32	11.771%	$98.7161	$98.72	$98.70	$98.70
Purchase #5	$215.51	7.616%	$231.9232	$231.92	$231.90	$231.90
Purchase #6	$141.83	3.544%	$146.8565	$146.86	$146.85	$146.90
Purchase #7	$91.64	13.686%	$104.1819	$104.18	$104.20	$104.20
7 purchase totals =	$710.32		$764.8349	$764.83	$764.75	$764.80