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	$185.33	4.788%	$194.2036	$194.20	$194.20	$194.20
Purchase #2	$22.72	13.345%	$25.752	$25.75	$25.75	$25.80
Purchase #3	$83.78	7.690%	$90.2227	$90.22	$90.20	$90.20
Purchase #4	$142.82	13.337%	$161.8679	$161.87	$161.85	$161.90
Purchase #5	$131.35	11.580%	$146.5603	$146.56	$146.55	$146.60
Purchase #6	$79.96	10.615%	$88.4478	$88.45	$88.45	$88.40
Purchase #7	$242.29	5.639%	$255.9527	$255.95	$255.95	$256.00
7 purchase totals =	$888.25		$963.0070	$963.00	$962.95	$963.10