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	$43.64	4.756%	$45.7155	$45.72	$45.70	$45.70
Purchase #2	$215.90	10.479%	$238.5242	$238.52	$238.50	$238.50
Purchase #3	$7.39	6.330%	$7.8578	$7.86	$7.85	$7.90
Purchase #4	$206.85	11.324%	$230.2737	$230.27	$230.25	$230.30
Purchase #5	$162.28	13.348%	$183.9411	$183.94	$183.95	$183.90
Purchase #6	$54.66	11.289%	$60.8306	$60.83	$60.85	$60.80
Purchase #7	$204.58	11.730%	$228.5772	$228.58	$228.60	$228.60
7 purchase totals =	$895.30		$995.7201	$995.72	$995.70	$995.70