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	$205.71	12.551%	$231.5287	$231.53	$231.55	$231.50
Purchase #2	$194.97	8.369%	$211.287	$211.29	$211.30	$211.30
Purchase #3	$100.72	4.398%	$105.1497	$105.15	$105.15	$105.10
Purchase #4	$131.44	10.666%	$145.4594	$145.46	$145.45	$145.50
Purchase #5	$162.70	4.191%	$169.5188	$169.52	$169.50	$169.50
Purchase #6	$240.66	13.343%	$272.7713	$272.77	$272.75	$272.80
Purchase #7	$138.50	9.640%	$151.8514	$151.85	$151.85	$151.90
7 purchase totals =	$1,174.70		$1,287.5663	$1,287.57	$1,287.55	$1,287.60