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	$101.95	3.111%	$105.1217	$105.12	$105.10	$105.10
Purchase #2	$40.59	4.739%	$42.5136	$42.51	$42.50	$42.50
Purchase #3	$109.66	7.396%	$117.7705	$117.77	$117.75	$117.80
Purchase #4	$65.80	10.791%	$72.9005	$72.90	$72.90	$72.90
Purchase #5	$18.35	8.373%	$19.8864	$19.89	$19.90	$19.90
Purchase #6	$182.41	12.572%	$205.3426	$205.34	$205.35	$205.30
Purchase #7	$166.68	8.436%	$180.7411	$180.74	$180.75	$180.70
7 purchase totals =	$685.44		$744.2764	$744.27	$744.25	$744.20