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	$50.66	8.233%	$54.8308	$54.83	$54.85	$54.80
Purchase #2	$68.53	7.558%	$73.7095	$73.71	$73.70	$73.70
Purchase #3	$35.62	4.734%	$37.3063	$37.31	$37.30	$37.30
Purchase #4	$11.67	7.382%	$12.5315	$12.53	$12.55	$12.50
Purchase #5	$48.78	13.412%	$55.3224	$55.32	$55.30	$55.30
Purchase #6	$233.83	3.745%	$242.5869	$242.59	$242.60	$242.60
Purchase #7	$194.48	12.235%	$218.2746	$218.27	$218.25	$218.30
7 purchase totals =	$643.57		$694.5620	$694.56	$694.55	$694.50