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	$64.54	4.315%	$67.3249	$67.32	$67.30	$67.30
Purchase #2	$163.59	10.390%	$180.587	$180.59	$180.60	$180.60
Purchase #3	$75.59	7.360%	$81.1534	$81.15	$81.15	$81.20
Purchase #4	$239.79	12.328%	$269.3513	$269.35	$269.35	$269.40
Purchase #5	$32.84	3.212%	$33.8948	$33.89	$33.90	$33.90
Purchase #6	$12.62	9.602%	$13.8318	$13.83	$13.85	$13.80
Purchase #7	$126.73	11.662%	$141.5093	$141.51	$141.50	$141.50
7 purchase totals =	$715.70		$787.6525	$787.64	$787.65	$787.70