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	$166.69	11.414%	$185.716	$185.72	$185.70	$185.70
Purchase #2	$127.64	11.143%	$141.8629	$141.86	$141.85	$141.90
Purchase #3	$117.87	6.323%	$125.3229	$125.32	$125.30	$125.30
Purchase #4	$58.75	13.183%	$66.495	$66.50	$66.50	$66.50
Purchase #5	$90.47	11.837%	$101.1789	$101.18	$101.20	$101.20
Purchase #6	$165.52	6.321%	$175.9825	$175.98	$176.00	$176.00
Purchase #7	$73.88	9.480%	$80.8838	$80.88	$80.90	$80.90
7 purchase totals =	$800.82		$877.4420	$877.44	$877.45	$877.50