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	$205.81	8.196%	$222.6782	$222.68	$222.70	$222.70
Purchase #2	$34.69	8.434%	$37.6158	$37.62	$37.60	$37.60
Purchase #3	$232.97	10.436%	$257.2827	$257.28	$257.30	$257.30
Purchase #4	$40.30	6.526%	$42.93	$42.93	$42.95	$42.90
Purchase #5	$176.54	3.297%	$182.3605	$182.36	$182.35	$182.40
Purchase #6	$221.88	5.256%	$233.542	$233.54	$233.55	$233.50
Purchase #7	$25.54	3.445%	$26.4199	$26.42	$26.40	$26.40
7 purchase totals =	$937.73		$1,002.8291	$1,002.83	$1,002.85	$1,002.80