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	$85.38	10.426%	$94.2817	$94.28	$94.30	$94.30
Purchase #2	$35.30	4.422%	$36.861	$36.86	$36.85	$36.90
Purchase #3	$215.76	3.176%	$222.6125	$222.61	$222.60	$222.60
Purchase #4	$147.69	12.680%	$166.4171	$166.42	$166.40	$166.40
Purchase #5	$123.96	7.280%	$132.9843	$132.98	$133.00	$133.00
Purchase #6	$45.58	10.317%	$50.2825	$50.28	$50.30	$50.30
Purchase #7	$172.40	4.147%	$179.5494	$179.55	$179.55	$179.50
7 purchase totals =	$826.07		$882.9885	$882.98	$883.00	$883.00