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	$141.62	11.468%	$157.861	$157.86	$157.85	$157.90
Purchase #2	$173.71	11.713%	$194.0567	$194.06	$194.05	$194.10
Purchase #3	$61.81	6.109%	$65.586	$65.59	$65.60	$65.60
Purchase #4	$104.46	4.845%	$109.5211	$109.52	$109.50	$109.50
Purchase #5	$39.76	3.744%	$41.2486	$41.25	$41.25	$41.20
Purchase #6	$166.77	3.758%	$173.0372	$173.04	$173.05	$173.00
Purchase #7	$249.78	11.307%	$278.0226	$278.02	$278.00	$278.00
7 purchase totals =	$937.91		$1,019.3332	$1,019.34	$1,019.30	$1,019.30