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	$241.29	10.391%	$266.3624	$266.36	$266.35	$266.40
Purchase #2	$101.75	11.679%	$113.6334	$113.63	$113.65	$113.60
Purchase #3	$146.70	3.670%	$152.0839	$152.08	$152.10	$152.10
Purchase #4	$183.36	4.371%	$191.3747	$191.37	$191.35	$191.40
Purchase #5	$72.32	5.512%	$76.3063	$76.31	$76.30	$76.30
Purchase #6	$211.55	10.478%	$233.7162	$233.72	$233.70	$233.70
Purchase #7	$24.58	13.865%	$27.988	$27.99	$28.00	$28.00
7 purchase totals =	$981.55		$1,061.4649	$1,061.46	$1,061.45	$1,061.50