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	$243.33	13.255%	$275.5834	$275.58	$275.60	$275.60
Purchase #2	$99.74	3.732%	$103.4623	$103.46	$103.45	$103.50
Purchase #3	$85.47	12.216%	$95.911	$95.91	$95.90	$95.90
Purchase #4	$214.79	4.516%	$224.4899	$224.49	$224.50	$224.50
Purchase #5	$215.74	13.404%	$244.6578	$244.66	$244.65	$244.70
Purchase #6	$83.53	6.265%	$88.7632	$88.76	$88.75	$88.80
Purchase #7	$145.94	3.756%	$151.4215	$151.42	$151.40	$151.40
7 purchase totals =	$1,088.54		$1,184.2891	$1,184.28	$1,184.25	$1,184.40