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	$183.32	12.228%	$205.7364	$205.74	$205.75	$205.70
Purchase #2	$37.76	4.240%	$39.361	$39.36	$39.35	$39.40
Purchase #3	$152.35	10.818%	$168.8312	$168.83	$168.85	$168.80
Purchase #4	$85.28	5.312%	$89.8101	$89.81	$89.80	$89.80
Purchase #5	$48.92	7.685%	$52.6795	$52.68	$52.70	$52.70
Purchase #6	$154.71	3.623%	$160.3151	$160.32	$160.30	$160.30
Purchase #7	$153.82	8.385%	$166.7178	$166.72	$166.70	$166.70
7 purchase totals =	$816.16		$883.4511	$883.46	$883.45	$883.40