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	$89.57	8.782%	$97.436	$97.44	$97.45	$97.40
Purchase #2	$6.66	8.515%	$7.2271	$7.23	$7.25	$7.20
Purchase #3	$43.71	6.588%	$46.5896	$46.59	$46.60	$46.60
Purchase #4	$188.76	7.780%	$203.4455	$203.45	$203.45	$203.40
Purchase #5	$141.40	7.381%	$151.8367	$151.84	$151.85	$151.80
Purchase #6	$57.57	5.814%	$60.9171	$60.92	$60.90	$60.90
Purchase #7	$144.76	4.684%	$151.5406	$151.54	$151.55	$151.50
7 purchase totals =	$672.43		$718.9926	$719.01	$719.05	$718.80