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	$223.94	5.535%	$236.3351	$236.34	$236.35	$236.30
Purchase #2	$59.51	10.395%	$65.6961	$65.70	$65.70	$65.70
Purchase #3	$35.37	9.234%	$38.6361	$38.64	$38.65	$38.60
Purchase #4	$171.64	9.840%	$188.5294	$188.53	$188.55	$188.50
Purchase #5	$230.34	9.218%	$251.5727	$251.57	$251.55	$251.60
Purchase #6	$204.56	10.152%	$225.3269	$225.33	$225.35	$225.30
Purchase #7	$51.53	11.770%	$57.5951	$57.60	$57.60	$57.60
7 purchase totals =	$976.89		$1,063.6914	$1,063.71	$1,063.75	$1,063.60