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	$182.44	9.657%	$200.0582	$200.06	$200.05	$200.10
Purchase #2	$38.34	10.471%	$42.3546	$42.35	$42.35	$42.40
Purchase #3	$79.60	7.228%	$85.3535	$85.35	$85.35	$85.40
Purchase #4	$139.77	4.874%	$146.5824	$146.58	$146.60	$146.60
Purchase #5	$6.69	11.268%	$7.4438	$7.44	$7.45	$7.40
Purchase #6	$155.58	8.176%	$168.3002	$168.30	$168.30	$168.30
Purchase #7	$22.76	6.305%	$24.195	$24.20	$24.20	$24.20
7 purchase totals =	$625.18		$674.2877	$674.28	$674.30	$674.40