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	$37.96	13.457%	$43.0683	$43.07	$43.05	$43.10
Purchase #2	$166.53	3.568%	$172.4718	$172.47	$172.45	$172.50
Purchase #3	$31.84	10.722%	$35.2539	$35.25	$35.25	$35.30
Purchase #4	$69.44	6.125%	$73.6932	$73.69	$73.70	$73.70
Purchase #5	$192.25	12.282%	$215.8621	$215.86	$215.85	$215.90
Purchase #6	$132.92	7.116%	$142.3786	$142.38	$142.40	$142.40
Purchase #7	$15.76	12.704%	$17.7622	$17.76	$17.75	$17.80
7 purchase totals =	$646.70		$700.4901	$700.48	$700.45	$700.70