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	$48.93	7.388%	$52.5449	$52.54	$52.55	$52.50
Purchase #2	$163.27	10.810%	$180.9195	$180.92	$180.90	$180.90
Purchase #3	$56.63	4.429%	$59.1381	$59.14	$59.15	$59.10
Purchase #4	$52.80	11.690%	$58.9723	$58.97	$58.95	$59.00
Purchase #5	$99.94	13.314%	$113.246	$113.25	$113.25	$113.20
Purchase #6	$246.67	5.242%	$259.6004	$259.60	$259.60	$259.60
Purchase #7	$245.95	10.492%	$271.7551	$271.76	$271.75	$271.80
7 purchase totals =	$914.19		$996.1763	$996.18	$996.15	$996.10