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	$184.84	11.401%	$205.9136	$205.91	$205.90	$205.90
Purchase #2	$145.66	13.594%	$165.461	$165.46	$165.45	$165.50
Purchase #3	$63.65	6.636%	$67.8738	$67.87	$67.85	$67.90
Purchase #4	$158.26	7.686%	$170.4239	$170.42	$170.40	$170.40
Purchase #5	$49.93	6.384%	$53.1175	$53.12	$53.10	$53.10
Purchase #6	$86.26	3.344%	$89.1445	$89.14	$89.15	$89.10
Purchase #7	$67.32	4.569%	$70.3959	$70.40	$70.40	$70.40
7 purchase totals =	$755.92		$822.3302	$822.32	$822.25	$822.30