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	$202.39	7.638%	$217.8485	$217.85	$217.85	$217.80
Purchase #2	$167.35	4.182%	$174.3486	$174.35	$174.35	$174.30
Purchase #3	$57.31	11.501%	$63.9012	$63.90	$63.90	$63.90
Purchase #4	$107.51	4.180%	$112.0039	$112.00	$112.00	$112.00
Purchase #5	$99.32	12.505%	$111.74	$111.74	$111.75	$111.70
Purchase #6	$105.73	13.568%	$120.0754	$120.08	$120.10	$120.10
Purchase #7	$87.60	13.840%	$99.7238	$99.72	$99.70	$99.70
7 purchase totals =	$827.21		$899.6414	$899.64	$899.65	$899.50