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	$104.75	6.534%	$111.5944	$111.59	$111.60	$111.60
Purchase #2	$169.58	8.769%	$184.4505	$184.45	$184.45	$184.50
Purchase #3	$242.75	4.689%	$254.1325	$254.13	$254.15	$254.10
Purchase #4	$179.83	3.852%	$186.7571	$186.76	$186.75	$186.80
Purchase #5	$234.65	6.689%	$250.3457	$250.35	$250.35	$250.30
Purchase #6	$210.57	12.352%	$236.5796	$236.58	$236.60	$236.60
Purchase #7	$20.30	3.702%	$21.0515	$21.05	$21.05	$21.10
7 purchase totals =	$1,162.43		$1,244.9113	$1,244.91	$1,244.95	$1,245.00