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	$51.57	3.795%	$53.5271	$53.53	$53.55	$53.50
Purchase #2	$228.50	5.194%	$240.3683	$240.37	$240.35	$240.40
Purchase #3	$91.69	9.166%	$100.0943	$100.09	$100.10	$100.10
Purchase #4	$38.92	12.374%	$43.736	$43.74	$43.75	$43.70
Purchase #5	$42.45	4.766%	$44.4732	$44.47	$44.45	$44.50
Purchase #6	$242.92	3.105%	$250.4627	$250.46	$250.45	$250.50
Purchase #7	$145.76	13.431%	$165.337	$165.34	$165.35	$165.30
7 purchase totals =	$841.81		$897.9986	$898.00	$898.00	$898.00