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	$178.52	10.580%	$197.4074	$197.41	$197.40	$197.40
Purchase #2	$99.90	11.439%	$111.3276	$111.33	$111.35	$111.30
Purchase #3	$31.28	4.434%	$32.667	$32.67	$32.65	$32.70
Purchase #4	$127.78	10.236%	$140.8596	$140.86	$140.85	$140.90
Purchase #5	$210.60	13.397%	$238.8141	$238.81	$238.80	$238.80
Purchase #6	$142.53	10.453%	$157.4287	$157.43	$157.45	$157.40
Purchase #7	$6.25	12.343%	$7.0214	$7.02	$7.00	$7.00
7 purchase totals =	$796.86		$885.5258	$885.53	$885.50	$885.50