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	$9.28	10.862%	$10.288	$10.29	$10.30	$10.30
Purchase #2	$158.38	3.554%	$164.0088	$164.01	$164.00	$164.00
Purchase #3	$81.95	4.462%	$85.6066	$85.61	$85.60	$85.60
Purchase #4	$72.44	13.831%	$82.4592	$82.46	$82.45	$82.50
Purchase #5	$134.61	13.225%	$152.4122	$152.41	$152.40	$152.40
Purchase #6	$55.58	7.181%	$59.5712	$59.57	$59.55	$59.60
Purchase #7	$150.94	5.559%	$159.3308	$159.33	$159.35	$159.30
7 purchase totals =	$663.18		$713.6768	$713.68	$713.65	$713.70