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	$215.83	9.653%	$236.6641	$236.66	$236.65	$236.70
Purchase #2	$152.76	8.342%	$165.5032	$165.50	$165.50	$165.50
Purchase #3	$201.89	7.817%	$217.6717	$217.67	$217.65	$217.70
Purchase #4	$79.92	4.514%	$83.5276	$83.53	$83.55	$83.50
Purchase #5	$34.75	9.599%	$38.0857	$38.09	$38.10	$38.10
Purchase #6	$64.56	4.207%	$67.276	$67.28	$67.30	$67.30
Purchase #7	$43.85	4.325%	$45.7465	$45.75	$45.75	$45.70
7 purchase totals =	$793.56		$854.4748	$854.48	$854.50	$854.50