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	$164.88	4.769%	$172.7431	$172.74	$172.75	$172.70
Purchase #2	$50.46	13.708%	$57.3771	$57.38	$57.40	$57.40
Purchase #3	$173.42	9.684%	$190.214	$190.21	$190.20	$190.20
Purchase #4	$48.86	7.640%	$52.5929	$52.59	$52.60	$52.60
Purchase #5	$102.95	9.550%	$112.7817	$112.78	$112.80	$112.80
Purchase #6	$164.60	9.708%	$180.5794	$180.58	$180.60	$180.60
Purchase #7	$36.83	13.645%	$41.8555	$41.86	$41.85	$41.90
7 purchase totals =	$742.00		$808.1437	$808.14	$808.20	$808.20