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	$117.52	12.254%	$131.9209	$131.92	$131.90	$131.90
Purchase #2	$210.54	7.543%	$226.421	$226.42	$226.40	$226.40
Purchase #3	$225.61	3.440%	$233.371	$233.37	$233.35	$233.40
Purchase #4	$99.91	8.422%	$108.3244	$108.32	$108.30	$108.30
Purchase #5	$95.95	9.522%	$105.0864	$105.09	$105.10	$105.10
Purchase #6	$148.31	11.600%	$165.514	$165.51	$165.50	$165.50
Purchase #7	$230.36	4.743%	$241.286	$241.29	$241.30	$241.30
7 purchase totals =	$1,128.20		$1,211.9237	$1,211.92	$1,211.85	$1,211.90