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	$235.88	4.678%	$246.9145	$246.91	$246.90	$246.90
Purchase #2	$168.83	13.536%	$191.6828	$191.68	$191.70	$191.70
Purchase #3	$92.50	3.673%	$95.8975	$95.90	$95.90	$95.90
Purchase #4	$9.42	12.552%	$10.6024	$10.60	$10.60	$10.60
Purchase #5	$99.68	4.660%	$104.3251	$104.33	$104.35	$104.30
Purchase #6	$106.30	13.613%	$120.7706	$120.77	$120.75	$120.80
Purchase #7	$220.83	12.844%	$249.1934	$249.19	$249.20	$249.20
7 purchase totals =	$933.44		$1,019.3863	$1,019.38	$1,019.40	$1,019.40