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	$54.79	12.418%	$61.5938	$61.59	$61.60	$61.60
Purchase #2	$67.74	4.519%	$70.8012	$70.80	$70.80	$70.80
Purchase #3	$162.75	10.564%	$179.9429	$179.94	$179.95	$179.90
Purchase #4	$111.73	5.857%	$118.274	$118.27	$118.25	$118.30
Purchase #5	$67.62	8.693%	$73.4982	$73.50	$73.50	$73.50
Purchase #6	$14.59	13.144%	$16.5077	$16.51	$16.50	$16.50
Purchase #7	$83.76	9.717%	$91.899	$91.90	$91.90	$91.90
7 purchase totals =	$562.98		$612.5168	$612.51	$612.50	$612.50