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	$69.47	12.108%	$77.8814	$77.88	$77.90	$77.90
Purchase #2	$144.48	13.662%	$164.2189	$164.22	$164.20	$164.20
Purchase #3	$244.28	5.154%	$256.8702	$256.87	$256.85	$256.90
Purchase #4	$179.53	8.429%	$194.6626	$194.66	$194.65	$194.70
Purchase #5	$31.62	6.305%	$33.6136	$33.61	$33.60	$33.60
Purchase #6	$86.86	10.178%	$95.7006	$95.70	$95.70	$95.70
Purchase #7	$183.38	7.229%	$196.6365	$196.64	$196.65	$196.60
7 purchase totals =	$939.62		$1,019.5838	$1,019.58	$1,019.55	$1,019.60