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	$179.41	6.185%	$190.5065	$190.51	$190.50	$190.50
Purchase #2	$178.39	6.766%	$190.4599	$190.46	$190.45	$190.50
Purchase #3	$102.98	4.227%	$107.333	$107.33	$107.35	$107.30
Purchase #4	$30.67	6.463%	$32.6522	$32.65	$32.65	$32.70
Purchase #5	$172.36	4.351%	$179.8594	$179.86	$179.85	$179.90
Purchase #6	$225.53	7.213%	$241.7975	$241.80	$241.80	$241.80
Purchase #7	$24.82	6.743%	$26.4936	$26.49	$26.50	$26.50
7 purchase totals =	$914.16		$969.1021	$969.10	$969.10	$969.20