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	$189.57	9.659%	$207.8806	$207.88	$207.90	$207.90
Purchase #2	$247.29	3.718%	$256.4842	$256.48	$256.50	$256.50
Purchase #3	$205.81	9.256%	$224.8598	$224.86	$224.85	$224.90
Purchase #4	$209.33	11.592%	$233.5955	$233.60	$233.60	$233.60
Purchase #5	$38.34	5.344%	$40.3889	$40.39	$40.40	$40.40
Purchase #6	$188.34	10.607%	$208.3172	$208.32	$208.30	$208.30
Purchase #7	$200.64	6.847%	$214.3778	$214.38	$214.40	$214.40
7 purchase totals =	$1,279.32		$1,385.9040	$1,385.91	$1,385.95	$1,386.00