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	$56.52	11.124%	$62.8073	$62.81	$62.80	$62.80
Purchase #2	$79.30	4.721%	$83.0438	$83.04	$83.05	$83.00
Purchase #3	$92.62	7.656%	$99.711	$99.71	$99.70	$99.70
Purchase #4	$57.73	7.277%	$61.931	$61.93	$61.95	$61.90
Purchase #5	$44.71	4.745%	$46.8315	$46.83	$46.85	$46.80
Purchase #6	$129.72	3.374%	$134.0968	$134.10	$134.10	$134.10
Purchase #7	$48.90	10.632%	$54.099	$54.10	$54.10	$54.10
7 purchase totals =	$509.50		$542.5204	$542.52	$542.55	$542.40