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	$44.32	3.497%	$45.8699	$45.87	$45.85	$45.90
Purchase #2	$98.49	11.128%	$109.45	$109.45	$109.45	$109.50
Purchase #3	$232.55	10.190%	$256.2468	$256.25	$256.25	$256.20
Purchase #4	$16.39	4.789%	$17.1749	$17.17	$17.15	$17.20
Purchase #5	$56.73	3.496%	$58.7133	$58.71	$58.70	$58.70
Purchase #6	$169.58	12.692%	$191.1031	$191.10	$191.10	$191.10
Purchase #7	$151.62	10.823%	$168.0298	$168.03	$168.05	$168.00
7 purchase totals =	$769.68		$846.5878	$846.58	$846.55	$846.60