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	$32.38	9.852%	$35.5701	$35.57	$35.55	$35.60
Purchase #2	$244.32	10.321%	$269.5363	$269.54	$269.55	$269.50
Purchase #3	$173.27	4.495%	$181.0585	$181.06	$181.05	$181.10
Purchase #4	$79.44	8.848%	$86.4689	$86.47	$86.45	$86.50
Purchase #5	$25.45	10.241%	$28.0563	$28.06	$28.05	$28.10
Purchase #6	$147.86	11.503%	$164.8683	$164.87	$164.85	$164.90
Purchase #7	$11.80	6.857%	$12.6091	$12.61	$12.60	$12.60
7 purchase totals =	$714.52		$778.1675	$778.18	$778.10	$778.30