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	$108.30	5.346%	$114.0897	$114.09	$114.10	$114.10
Purchase #2	$10.32	6.720%	$11.0135	$11.01	$11.00	$11.00
Purchase #3	$173.62	6.501%	$184.907	$184.91	$184.90	$184.90
Purchase #4	$79.81	7.239%	$85.5874	$85.59	$85.60	$85.60
Purchase #5	$111.29	5.171%	$117.0448	$117.04	$117.05	$117.00
Purchase #6	$159.75	11.787%	$178.5797	$178.58	$178.60	$178.60
Purchase #7	$102.86	6.236%	$109.2743	$109.27	$109.25	$109.30
7 purchase totals =	$745.95		$800.4964	$800.49	$800.50	$800.50