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	$176.77	11.174%	$196.5223	$196.52	$196.50	$196.50
Purchase #2	$38.40	9.269%	$41.9593	$41.96	$41.95	$42.00
Purchase #3	$170.74	12.133%	$191.4559	$191.46	$191.45	$191.50
Purchase #4	$205.31	12.716%	$231.4172	$231.42	$231.40	$231.40
Purchase #5	$174.50	7.517%	$187.6172	$187.62	$187.60	$187.60
Purchase #6	$9.92	6.793%	$10.5939	$10.59	$10.60	$10.60
Purchase #7	$122.41	8.260%	$132.5211	$132.52	$132.50	$132.50
7 purchase totals =	$898.05		$992.0869	$992.09	$992.00	$992.10