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	$66.74	8.751%	$72.5804	$72.58	$72.60	$72.60
Purchase #2	$98.94	4.518%	$103.4101	$103.41	$103.40	$103.40
Purchase #3	$99.61	11.524%	$111.0891	$111.09	$111.10	$111.10
Purchase #4	$125.49	9.589%	$137.5232	$137.52	$137.50	$137.50
Purchase #5	$191.42	5.373%	$201.705	$201.71	$201.70	$201.70
Purchase #6	$6.34	9.439%	$6.9384	$6.94	$6.95	$6.90
Purchase #7	$230.47	8.805%	$250.7629	$250.76	$250.75	$250.80
7 purchase totals =	$819.01		$884.0091	$884.01	$884.00	$884.00