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	$40.27	13.285%	$45.6199	$45.62	$45.60	$45.60
Purchase #2	$48.80	13.566%	$55.4202	$55.42	$55.40	$55.40
Purchase #3	$193.52	3.830%	$200.9318	$200.93	$200.95	$200.90
Purchase #4	$19.69	6.340%	$20.9383	$20.94	$20.95	$20.90
Purchase #5	$41.30	4.454%	$43.1395	$43.14	$43.15	$43.10
Purchase #6	$230.71	10.289%	$254.4478	$254.45	$254.45	$254.40
Purchase #7	$199.99	3.138%	$206.2657	$206.27	$206.25	$206.30
7 purchase totals =	$774.28		$826.7632	$826.77	$826.75	$826.60