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	$42.34	9.156%	$46.2167	$46.22	$46.20	$46.20
Purchase #2	$103.94	3.825%	$107.9157	$107.92	$107.90	$107.90
Purchase #3	$74.32	8.478%	$80.6208	$80.62	$80.60	$80.60
Purchase #4	$119.74	9.286%	$130.8591	$130.86	$130.85	$130.90
Purchase #5	$64.66	12.766%	$72.9145	$72.91	$72.90	$72.90
Purchase #6	$97.42	6.622%	$103.8712	$103.87	$103.85	$103.90
Purchase #7	$165.34	6.140%	$175.4919	$175.49	$175.50	$175.50
7 purchase totals =	$667.76		$717.8899	$717.89	$717.80	$717.90