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	$58.50	11.513%	$65.2351	$65.24	$65.25	$65.20
Purchase #2	$88.73	13.660%	$100.8505	$100.85	$100.85	$100.90
Purchase #3	$25.77	6.258%	$27.3827	$27.38	$27.40	$27.40
Purchase #4	$38.93	9.199%	$42.5112	$42.51	$42.50	$42.50
Purchase #5	$198.25	6.268%	$210.6763	$210.68	$210.70	$210.70
Purchase #6	$113.68	11.170%	$126.3781	$126.38	$126.40	$126.40
Purchase #7	$41.31	4.463%	$43.1537	$43.15	$43.15	$43.20
7 purchase totals =	$565.17		$616.1876	$616.19	$616.25	$616.30