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	$42.87	6.457%	$45.6381	$45.64	$45.65	$45.60
Purchase #2	$73.73	5.697%	$77.9304	$77.93	$77.95	$77.90
Purchase #3	$125.45	13.799%	$142.7608	$142.76	$142.75	$142.80
Purchase #4	$119.80	9.841%	$131.5895	$131.59	$131.60	$131.60
Purchase #5	$45.86	6.375%	$48.7836	$48.78	$48.80	$48.80
Purchase #6	$105.92	5.163%	$111.3886	$111.39	$111.40	$111.40
Purchase #7	$173.55	9.471%	$189.9869	$189.99	$190.00	$190.00
7 purchase totals =	$687.18		$748.0779	$748.08	$748.15	$748.10