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	$126.30	6.319%	$134.2809	$134.28	$134.30	$134.30
Purchase #2	$39.95	9.166%	$43.6118	$43.61	$43.60	$43.60
Purchase #3	$81.26	13.770%	$92.4495	$92.45	$92.45	$92.40
Purchase #4	$7.81	7.128%	$8.3667	$8.37	$8.35	$8.40
Purchase #5	$86.82	10.824%	$96.2174	$96.22	$96.20	$96.20
Purchase #6	$52.90	13.543%	$60.0642	$60.06	$60.05	$60.10
Purchase #7	$40.85	3.267%	$42.1846	$42.18	$42.20	$42.20
7 purchase totals =	$435.89		$477.1751	$477.17	$477.15	$477.20