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	$129.47	13.722%	$147.2359	$147.24	$147.25	$147.20
Purchase #2	$154.74	12.359%	$173.8643	$173.86	$173.85	$173.90
Purchase #3	$58.75	3.532%	$60.8251	$60.83	$60.85	$60.80
Purchase #4	$82.60	10.245%	$91.0624	$91.06	$91.05	$91.10
Purchase #5	$81.29	11.499%	$90.6375	$90.64	$90.65	$90.60
Purchase #6	$141.81	11.812%	$158.5606	$158.56	$158.55	$158.60
Purchase #7	$27.69	4.636%	$28.9737	$28.97	$28.95	$29.00
7 purchase totals =	$676.35		$751.1595	$751.16	$751.15	$751.20