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	$222.52	10.589%	$246.0826	$246.08	$246.10	$246.10
Purchase #2	$219.41	8.514%	$238.0906	$238.09	$238.10	$238.10
Purchase #3	$211.89	11.316%	$235.8675	$235.87	$235.85	$235.90
Purchase #4	$134.86	12.761%	$152.0695	$152.07	$152.05	$152.10
Purchase #5	$19.69	8.217%	$21.3079	$21.31	$21.30	$21.30
Purchase #6	$9.50	10.543%	$10.5016	$10.50	$10.50	$10.50
Purchase #7	$87.27	3.762%	$90.5531	$90.55	$90.55	$90.60
7 purchase totals =	$905.14		$994.4728	$994.47	$994.45	$994.60