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	$160.73	6.605%	$171.3462	$171.35	$171.35	$171.30
Purchase #2	$34.90	6.513%	$37.173	$37.17	$37.15	$37.20
Purchase #3	$88.84	4.109%	$92.4904	$92.49	$92.50	$92.50
Purchase #4	$226.88	12.421%	$255.0608	$255.06	$255.05	$255.10
Purchase #5	$155.71	7.221%	$166.9538	$166.95	$166.95	$167.00
Purchase #6	$126.89	9.660%	$139.1476	$139.15	$139.15	$139.10
Purchase #7	$7.62	6.486%	$8.1142	$8.11	$8.10	$8.10
7 purchase totals =	$801.57		$870.2860	$870.28	$870.25	$870.30