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	$81.56	11.751%	$91.1441	$91.14	$91.15	$91.10
Purchase #2	$18.98	3.855%	$19.7117	$19.71	$19.70	$19.70
Purchase #3	$12.30	10.870%	$13.637	$13.64	$13.65	$13.60
Purchase #4	$87.31	7.730%	$94.0591	$94.06	$94.05	$94.10
Purchase #5	$137.55	10.579%	$152.1014	$152.10	$152.10	$152.10
Purchase #6	$42.52	4.371%	$44.3785	$44.38	$44.40	$44.40
Purchase #7	$98.79	10.389%	$109.0533	$109.05	$109.05	$109.10
7 purchase totals =	$479.01		$524.0851	$524.08	$524.10	$524.10