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	$100.30	10.690%	$111.0221	$111.02	$111.00	$111.00
Purchase #2	$158.94	3.486%	$164.4806	$164.48	$164.50	$164.50
Purchase #3	$99.30	5.752%	$105.0117	$105.01	$105.00	$105.00
Purchase #4	$86.60	11.633%	$96.6742	$96.67	$96.65	$96.70
Purchase #5	$48.71	7.251%	$52.242	$52.24	$52.25	$52.20
Purchase #6	$89.72	12.193%	$100.6596	$100.66	$100.65	$100.70
Purchase #7	$94.33	8.518%	$102.365	$102.37	$102.35	$102.40
7 purchase totals =	$677.90		$732.4552	$732.45	$732.40	$732.50