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	$183.72	13.778%	$209.0329	$209.03	$209.05	$209.00
Purchase #2	$190.27	4.776%	$199.3573	$199.36	$199.35	$199.40
Purchase #3	$11.99	4.431%	$12.5213	$12.52	$12.50	$12.50
Purchase #4	$33.30	13.641%	$37.8425	$37.84	$37.85	$37.80
Purchase #5	$176.76	7.485%	$189.9905	$189.99	$190.00	$190.00
Purchase #6	$166.51	8.727%	$181.0413	$181.04	$181.05	$181.00
Purchase #7	$131.31	6.217%	$139.4735	$139.47	$139.45	$139.50
7 purchase totals =	$893.86		$969.2593	$969.25	$969.25	$969.20