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	$54.96	7.849%	$59.2738	$59.27	$59.25	$59.30
Purchase #2	$12.72	7.396%	$13.6608	$13.66	$13.65	$13.70
Purchase #3	$38.42	6.141%	$40.7794	$40.78	$40.80	$40.80
Purchase #4	$29.87	9.270%	$32.6389	$32.64	$32.65	$32.60
Purchase #5	$185.65	7.343%	$199.2823	$199.28	$199.30	$199.30
Purchase #6	$7.40	11.678%	$8.2642	$8.26	$8.25	$8.30
Purchase #7	$56.66	8.104%	$61.2517	$61.25	$61.25	$61.30
7 purchase totals =	$385.68		$415.1511	$415.14	$415.15	$415.30