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	$205.30	8.516%	$222.7833	$222.78	$222.80	$222.80
Purchase #2	$37.43	7.391%	$40.1965	$40.20	$40.20	$40.20
Purchase #3	$234.98	9.309%	$256.8543	$256.85	$256.85	$256.90
Purchase #4	$12.62	6.272%	$13.4115	$13.41	$13.40	$13.40
Purchase #5	$249.80	11.714%	$279.0616	$279.06	$279.05	$279.10
Purchase #6	$95.62	8.397%	$103.6492	$103.65	$103.65	$103.60
Purchase #7	$96.65	6.639%	$103.0666	$103.07	$103.05	$103.10
7 purchase totals =	$932.40		$1,019.0230	$1,019.02	$1,019.00	$1,019.10