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	$155.52	12.257%	$174.5821	$174.58	$174.60	$174.60
Purchase #2	$80.96	10.422%	$89.3977	$89.40	$89.40	$89.40
Purchase #3	$129.69	11.308%	$144.3553	$144.36	$144.35	$144.40
Purchase #4	$187.66	3.429%	$194.0949	$194.09	$194.10	$194.10
Purchase #5	$215.40	9.442%	$235.7381	$235.74	$235.75	$235.70
Purchase #6	$141.25	13.748%	$160.6691	$160.67	$160.65	$160.70
Purchase #7	$177.41	7.413%	$190.5614	$190.56	$190.55	$190.60
7 purchase totals =	$1,087.89		$1,189.3986	$1,189.40	$1,189.40	$1,189.50