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	$176.97	10.845%	$196.1624	$196.16	$196.15	$196.20
Purchase #2	$92.83	9.360%	$101.5189	$101.52	$101.50	$101.50
Purchase #3	$28.25	6.440%	$30.0693	$30.07	$30.05	$30.10
Purchase #4	$154.83	13.792%	$176.1842	$176.18	$176.20	$176.20
Purchase #5	$134.85	13.151%	$152.5841	$152.58	$152.60	$152.60
Purchase #6	$99.66	3.260%	$102.9089	$102.91	$102.90	$102.90
Purchase #7	$155.37	4.833%	$162.879	$162.88	$162.90	$162.90
7 purchase totals =	$842.76		$922.3068	$922.30	$922.30	$922.40