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	$69.94	4.173%	$72.8586	$72.86	$72.85	$72.90
Purchase #2	$25.73	12.655%	$28.9861	$28.99	$29.00	$29.00
Purchase #3	$237.28	8.754%	$258.0515	$258.05	$258.05	$258.10
Purchase #4	$150.83	11.636%	$168.3806	$168.38	$168.40	$168.40
Purchase #5	$148.65	4.822%	$155.8179	$155.82	$155.80	$155.80
Purchase #6	$242.59	10.251%	$267.4579	$267.46	$267.45	$267.50
Purchase #7	$159.83	3.279%	$165.0708	$165.07	$165.05	$165.10
7 purchase totals =	$1,034.85		$1,116.6234	$1,116.63	$1,116.60	$1,116.80