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	$86.45	10.517%	$95.5419	$95.54	$95.55	$95.50
Purchase #2	$76.66	13.291%	$86.8489	$86.85	$86.85	$86.80
Purchase #3	$159.83	3.473%	$165.3809	$165.38	$165.40	$165.40
Purchase #4	$215.56	12.573%	$242.6624	$242.66	$242.65	$242.70
Purchase #5	$51.47	9.568%	$56.3946	$56.39	$56.40	$56.40
Purchase #6	$37.55	6.499%	$39.9904	$39.99	$40.00	$40.00
Purchase #7	$85.62	5.106%	$89.9918	$89.99	$90.00	$90.00
7 purchase totals =	$713.14		$776.8109	$776.80	$776.85	$776.80