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	$223.30	3.829%	$231.8502	$231.85	$231.85	$231.90
Purchase #2	$208.49	6.278%	$221.579	$221.58	$221.60	$221.60
Purchase #3	$46.44	13.648%	$52.7781	$52.78	$52.80	$52.80
Purchase #4	$107.83	4.227%	$112.388	$112.39	$112.40	$112.40
Purchase #5	$126.40	3.784%	$131.183	$131.18	$131.20	$131.20
Purchase #6	$184.87	13.800%	$210.3821	$210.38	$210.40	$210.40
Purchase #7	$207.32	10.678%	$229.4576	$229.46	$229.45	$229.50
7 purchase totals =	$1,104.65		$1,189.6180	$1,189.62	$1,189.70	$1,189.80