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	$81.27	5.598%	$85.8195	$85.82	$85.80	$85.80
Purchase #2	$178.60	10.182%	$196.7851	$196.79	$196.80	$196.80
Purchase #3	$91.25	6.372%	$97.0645	$97.06	$97.05	$97.10
Purchase #4	$172.34	4.403%	$179.9281	$179.93	$179.95	$179.90
Purchase #5	$54.87	10.119%	$60.4223	$60.42	$60.40	$60.40
Purchase #6	$235.48	12.859%	$265.7604	$265.76	$265.75	$265.80
Purchase #7	$233.92	3.235%	$241.4873	$241.49	$241.50	$241.50
7 purchase totals =	$1,047.73		$1,127.2672	$1,127.27	$1,127.25	$1,127.30