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	$209.60	6.292%	$222.788	$222.79	$222.80	$222.80
Purchase #2	$82.92	8.730%	$90.1589	$90.16	$90.15	$90.20
Purchase #3	$219.59	9.834%	$241.1845	$241.18	$241.20	$241.20
Purchase #4	$147.38	8.102%	$159.3207	$159.32	$159.30	$159.30
Purchase #5	$206.25	8.107%	$222.9707	$222.97	$222.95	$223.00
Purchase #6	$235.91	7.196%	$252.8861	$252.89	$252.90	$252.90
Purchase #7	$210.81	13.742%	$239.7795	$239.78	$239.80	$239.80
7 purchase totals =	$1,312.46		$1,429.0884	$1,429.09	$1,429.10	$1,429.20