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	$42.64	4.208%	$44.4343	$44.43	$44.45	$44.40
Purchase #2	$183.40	4.243%	$191.1817	$191.18	$191.20	$191.20
Purchase #3	$51.61	8.427%	$55.9592	$55.96	$55.95	$56.00
Purchase #4	$134.60	11.496%	$150.0736	$150.07	$150.05	$150.10
Purchase #5	$162.97	6.364%	$173.3414	$173.34	$173.35	$173.30
Purchase #6	$88.97	12.824%	$100.3795	$100.38	$100.40	$100.40
Purchase #7	$73.72	5.218%	$77.5667	$77.57	$77.55	$77.60
7 purchase totals =	$737.91		$792.9364	$792.93	$792.95	$793.00