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	$201.51	4.179%	$209.9311	$209.93	$209.95	$209.90
Purchase #2	$134.83	7.754%	$145.2847	$145.28	$145.30	$145.30
Purchase #3	$123.65	8.190%	$133.7769	$133.78	$133.80	$133.80
Purchase #4	$53.34	13.618%	$60.6038	$60.60	$60.60	$60.60
Purchase #5	$165.85	11.375%	$184.7154	$184.72	$184.70	$184.70
Purchase #6	$200.55	9.219%	$219.0387	$219.04	$219.05	$219.00
Purchase #7	$99.45	12.185%	$111.568	$111.57	$111.55	$111.60
7 purchase totals =	$979.18		$1,064.9186	$1,064.92	$1,064.95	$1,064.90