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	$199.49	13.824%	$227.0675	$227.07	$227.05	$227.10
Purchase #2	$182.69	9.250%	$199.5888	$199.59	$199.60	$199.60
Purchase #3	$99.94	11.727%	$111.66	$111.66	$111.65	$111.70
Purchase #4	$82.69	10.238%	$91.1558	$91.16	$91.15	$91.20
Purchase #5	$27.36	8.585%	$29.7089	$29.71	$29.70	$29.70
Purchase #6	$174.42	5.786%	$184.5119	$184.51	$184.50	$184.50
Purchase #7	$31.99	4.643%	$33.4753	$33.48	$33.50	$33.50
7 purchase totals =	$798.58		$877.1682	$877.18	$877.15	$877.30