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	$64.67	13.553%	$73.4347	$73.43	$73.45	$73.40
Purchase #2	$38.71	12.321%	$43.4795	$43.48	$43.50	$43.50
Purchase #3	$37.72	7.844%	$40.6788	$40.68	$40.70	$40.70
Purchase #4	$182.89	8.847%	$199.0703	$199.07	$199.05	$199.10
Purchase #5	$182.80	6.251%	$194.2268	$194.23	$194.25	$194.20
Purchase #6	$89.31	3.565%	$92.4939	$92.49	$92.50	$92.50
Purchase #7	$61.37	6.871%	$65.5867	$65.59	$65.60	$65.60
7 purchase totals =	$657.47		$708.9707	$708.97	$709.05	$709.00