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	$238.71	10.784%	$264.4525	$264.45	$264.45	$264.50
Purchase #2	$125.83	10.702%	$139.2963	$139.30	$139.30	$139.30
Purchase #3	$242.88	6.678%	$259.0995	$259.10	$259.10	$259.10
Purchase #4	$86.41	7.531%	$92.9175	$92.92	$92.90	$92.90
Purchase #5	$74.83	9.633%	$82.0384	$82.04	$82.05	$82.00
Purchase #6	$10.76	8.339%	$11.6573	$11.66	$11.65	$11.70
Purchase #7	$117.37	11.144%	$130.4497	$130.45	$130.45	$130.40
7 purchase totals =	$896.79		$979.9112	$979.92	$979.90	$979.90