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	$228.72	9.258%	$249.8949	$249.89	$249.90	$249.90
Purchase #2	$12.98	7.535%	$13.958	$13.96	$13.95	$14.00
Purchase #3	$163.34	7.785%	$176.056	$176.06	$176.05	$176.10
Purchase #4	$99.81	11.631%	$111.4189	$111.42	$111.40	$111.40
Purchase #5	$145.61	4.145%	$151.6455	$151.65	$151.65	$151.60
Purchase #6	$125.87	4.620%	$131.6852	$131.69	$131.70	$131.70
Purchase #7	$25.92	9.592%	$28.4062	$28.41	$28.40	$28.40
7 purchase totals =	$802.25		$863.0647	$863.08	$863.05	$863.10