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	$7.82	10.250%	$8.6216	$8.62	$8.60	$8.60
Purchase #2	$34.88	6.863%	$37.2738	$37.27	$37.25	$37.30
Purchase #3	$172.60	4.642%	$180.6121	$180.61	$180.60	$180.60
Purchase #4	$127.61	3.108%	$131.5761	$131.58	$131.60	$131.60
Purchase #5	$19.89	10.233%	$21.9253	$21.93	$21.95	$21.90
Purchase #6	$191.57	4.853%	$200.8669	$200.87	$200.85	$200.90
Purchase #7	$162.79	13.740%	$185.1573	$185.16	$185.15	$185.20
7 purchase totals =	$717.16		$766.0331	$766.04	$766.00	$766.10