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	$212.67	9.848%	$233.6137	$233.61	$233.60	$233.60
Purchase #2	$40.33	13.844%	$45.9133	$45.91	$45.90	$45.90
Purchase #3	$116.78	10.387%	$128.9099	$128.91	$128.90	$128.90
Purchase #4	$93.38	3.173%	$96.3429	$96.34	$96.35	$96.30
Purchase #5	$112.25	3.411%	$116.0788	$116.08	$116.10	$116.10
Purchase #6	$236.66	9.834%	$259.9331	$259.93	$259.95	$259.90
Purchase #7	$211.66	3.325%	$218.6977	$218.70	$218.70	$218.70
7 purchase totals =	$1,023.73		$1,099.4894	$1,099.48	$1,099.50	$1,099.40