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	$165.89	9.303%	$181.3227	$181.32	$181.30	$181.30
Purchase #2	$32.91	9.406%	$36.0055	$36.01	$36.00	$36.00
Purchase #3	$63.71	5.513%	$67.2223	$67.22	$67.20	$67.20
Purchase #4	$205.40	10.551%	$227.0718	$227.07	$227.05	$227.10
Purchase #5	$65.75	10.562%	$72.6945	$72.69	$72.70	$72.70
Purchase #6	$58.91	6.454%	$62.7121	$62.71	$62.70	$62.70
Purchase #7	$92.87	13.708%	$105.6006	$105.60	$105.60	$105.60
7 purchase totals =	$685.44		$752.6295	$752.62	$752.55	$752.60