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	$29.66	12.872%	$33.4778	$33.48	$33.50	$33.50
Purchase #2	$54.66	8.854%	$59.4996	$59.50	$59.50	$59.50
Purchase #3	$170.48	11.745%	$190.5029	$190.50	$190.50	$190.50
Purchase #4	$18.27	7.273%	$19.5988	$19.60	$19.60	$19.60
Purchase #5	$15.33	11.570%	$17.1037	$17.10	$17.10	$17.10
Purchase #6	$219.49	10.847%	$243.2981	$243.30	$243.30	$243.30
Purchase #7	$143.78	6.135%	$152.6009	$152.60	$152.60	$152.60
7 purchase totals =	$651.67		$716.0818	$716.08	$716.10	$716.10