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	$80.77	10.750%	$89.4528	$89.45	$89.45	$89.50
Purchase #2	$35.97	3.738%	$37.3146	$37.31	$37.30	$37.30
Purchase #3	$82.82	4.796%	$86.792	$86.79	$86.80	$86.80
Purchase #4	$241.71	13.384%	$274.0605	$274.06	$274.05	$274.10
Purchase #5	$122.37	3.240%	$126.3348	$126.33	$126.35	$126.30
Purchase #6	$65.66	5.142%	$69.0362	$69.04	$69.05	$69.00
Purchase #7	$70.44	4.435%	$73.564	$73.56	$73.55	$73.60
7 purchase totals =	$699.74		$756.5549	$756.54	$756.55	$756.60