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	$162.31	11.412%	$180.8328	$180.83	$180.85	$180.80
Purchase #2	$72.97	6.825%	$77.9502	$77.95	$77.95	$78.00
Purchase #3	$118.27	8.161%	$127.922	$127.92	$127.90	$127.90
Purchase #4	$136.66	13.650%	$155.3141	$155.31	$155.30	$155.30
Purchase #5	$89.38	7.654%	$96.2211	$96.22	$96.20	$96.20
Purchase #6	$54.37	3.235%	$56.1289	$56.13	$56.15	$56.10
Purchase #7	$20.95	9.280%	$22.8942	$22.89	$22.90	$22.90
7 purchase totals =	$654.91		$717.2633	$717.25	$717.25	$717.20