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	$94.49	9.791%	$103.7415	$103.74	$103.75	$103.70
Purchase #2	$14.33	3.164%	$14.7834	$14.78	$14.80	$14.80
Purchase #3	$239.78	6.753%	$255.9723	$255.97	$255.95	$256.00
Purchase #4	$133.33	9.754%	$146.335	$146.34	$146.35	$146.30
Purchase #5	$37.92	10.440%	$41.8788	$41.88	$41.90	$41.90
Purchase #6	$114.26	7.763%	$123.13	$123.13	$123.15	$123.10
Purchase #7	$76.50	5.571%	$80.7618	$80.76	$80.75	$80.80
7 purchase totals =	$710.61		$766.6028	$766.60	$766.65	$766.60