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	$194.52	7.708%	$209.5136	$209.51	$209.50	$209.50
Purchase #2	$246.85	7.719%	$265.9044	$265.90	$265.90	$265.90
Purchase #3	$182.94	4.785%	$191.6937	$191.69	$191.70	$191.70
Purchase #4	$155.70	8.274%	$168.5826	$168.58	$168.60	$168.60
Purchase #5	$57.97	3.308%	$59.8876	$59.89	$59.90	$59.90
Purchase #6	$233.47	7.849%	$251.7951	$251.80	$251.80	$251.80
Purchase #7	$123.29	7.510%	$132.5491	$132.55	$132.55	$132.50
7 purchase totals =	$1,194.74		$1,279.9261	$1,279.92	$1,279.95	$1,279.90