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	$77.83	10.451%	$85.964	$85.96	$85.95	$86.00
Purchase #2	$25.80	8.548%	$28.0054	$28.01	$28.00	$28.00
Purchase #3	$10.81	12.553%	$12.167	$12.17	$12.15	$12.20
Purchase #4	$49.38	9.488%	$54.0652	$54.07	$54.05	$54.10
Purchase #5	$188.40	12.349%	$211.6655	$211.67	$211.65	$211.70
Purchase #6	$86.75	3.104%	$89.4427	$89.44	$89.45	$89.40
Purchase #7	$173.30	9.412%	$189.611	$189.61	$189.60	$189.60
7 purchase totals =	$612.27		$670.9208	$670.93	$670.85	$671.00