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	$87.91	9.700%	$96.4373	$96.44	$96.45	$96.40
Purchase #2	$52.59	6.462%	$55.9884	$55.99	$56.00	$56.00
Purchase #3	$118.27	4.230%	$123.2728	$123.27	$123.25	$123.30
Purchase #4	$108.49	7.632%	$116.77	$116.77	$116.75	$116.80
Purchase #5	$85.56	6.116%	$90.7928	$90.79	$90.80	$90.80
Purchase #6	$147.43	10.456%	$162.8453	$162.85	$162.85	$162.80
Purchase #7	$9.69	3.577%	$10.0366	$10.04	$10.05	$10.00
7 purchase totals =	$609.94		$656.1432	$656.15	$656.15	$656.10