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	$206.58	11.788%	$230.9317	$230.93	$230.95	$230.90
Purchase #2	$20.46	5.518%	$21.589	$21.59	$21.60	$21.60
Purchase #3	$117.97	4.439%	$123.2067	$123.21	$123.20	$123.20
Purchase #4	$126.83	12.792%	$143.0541	$143.05	$143.05	$143.10
Purchase #5	$18.56	11.275%	$20.6526	$20.65	$20.65	$20.70
Purchase #6	$62.60	3.563%	$64.8304	$64.83	$64.85	$64.80
Purchase #7	$58.56	10.398%	$64.6491	$64.65	$64.65	$64.60
7 purchase totals =	$611.56		$668.9136	$668.91	$668.95	$668.90