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	$94.54	8.809%	$102.868	$102.87	$102.85	$102.90
Purchase #2	$48.78	8.199%	$52.7795	$52.78	$52.80	$52.80
Purchase #3	$51.99	10.303%	$57.3465	$57.35	$57.35	$57.30
Purchase #4	$45.90	6.465%	$48.8674	$48.87	$48.85	$48.90
Purchase #5	$172.60	11.161%	$191.8639	$191.86	$191.85	$191.90
Purchase #6	$91.68	13.415%	$103.9789	$103.98	$104.00	$104.00
Purchase #7	$162.69	4.190%	$169.5067	$169.51	$169.50	$169.50
7 purchase totals =	$668.18		$727.2109	$727.22	$727.20	$727.30