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	$169.56	11.617%	$189.2578	$189.26	$189.25	$189.30
Purchase #2	$82.56	7.668%	$88.8907	$88.89	$88.90	$88.90
Purchase #3	$226.27	5.490%	$238.6922	$238.69	$238.70	$238.70
Purchase #4	$190.42	11.170%	$211.6899	$211.69	$211.70	$211.70
Purchase #5	$107.32	4.308%	$111.9433	$111.94	$111.95	$111.90
Purchase #6	$165.50	10.728%	$183.2548	$183.25	$183.25	$183.30
Purchase #7	$171.92	10.866%	$190.6008	$190.60	$190.60	$190.60
7 purchase totals =	$1,113.55		$1,214.3295	$1,214.32	$1,214.35	$1,214.40