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	$201.72	10.195%	$222.2854	$222.29	$222.30	$222.30
Purchase #2	$182.33	6.537%	$194.2489	$194.25	$194.25	$194.20
Purchase #3	$209.61	9.122%	$228.7306	$228.73	$228.75	$228.70
Purchase #4	$72.66	12.337%	$81.6241	$81.62	$81.60	$81.60
Purchase #5	$66.49	8.380%	$72.0619	$72.06	$72.05	$72.10
Purchase #6	$36.81	3.678%	$38.1639	$38.16	$38.15	$38.20
Purchase #7	$223.93	3.508%	$231.7855	$231.79	$231.80	$231.80
7 purchase totals =	$993.55		$1,068.9003	$1,068.90	$1,068.90	$1,068.90