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	$175.73	9.474%	$192.3787	$192.38	$192.40	$192.40
Purchase #2	$100.95	10.541%	$111.5911	$111.59	$111.60	$111.60
Purchase #3	$28.67	5.166%	$30.1511	$30.15	$30.15	$30.20
Purchase #4	$141.72	7.621%	$152.5205	$152.52	$152.50	$152.50
Purchase #5	$68.88	12.790%	$77.6898	$77.69	$77.70	$77.70
Purchase #6	$37.30	11.141%	$41.4556	$41.46	$41.45	$41.50
Purchase #7	$150.31	13.265%	$170.2486	$170.25	$170.25	$170.20
7 purchase totals =	$703.56		$776.0354	$776.04	$776.05	$776.10