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	$185.55	3.292%	$191.6583	$191.66	$191.65	$191.70
Purchase #2	$58.72	11.753%	$65.6214	$65.62	$65.60	$65.60
Purchase #3	$123.81	13.404%	$140.4055	$140.41	$140.40	$140.40
Purchase #4	$217.25	3.346%	$224.5192	$224.52	$224.50	$224.50
Purchase #5	$229.66	12.833%	$259.1323	$259.13	$259.15	$259.10
Purchase #6	$144.40	4.264%	$150.5572	$150.56	$150.55	$150.60
Purchase #7	$139.50	10.599%	$154.2856	$154.29	$154.30	$154.30
7 purchase totals =	$1,098.89		$1,186.1795	$1,186.19	$1,186.15	$1,186.20