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	$110.81	13.673%	$125.9611	$125.96	$125.95	$126.00
Purchase #2	$167.31	3.640%	$173.4001	$173.40	$173.40	$173.40
Purchase #3	$134.38	10.579%	$148.5961	$148.60	$148.60	$148.60
Purchase #4	$16.51	9.740%	$18.1181	$18.12	$18.10	$18.10
Purchase #5	$176.71	11.133%	$196.3831	$196.38	$196.40	$196.40
Purchase #6	$98.35	5.532%	$103.7907	$103.79	$103.80	$103.80
Purchase #7	$37.83	5.237%	$39.8112	$39.81	$39.80	$39.80
7 purchase totals =	$741.90		$806.0604	$806.06	$806.05	$806.10