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	$131.68	4.652%	$137.8058	$137.81	$137.80	$137.80
Purchase #2	$202.54	5.784%	$214.2549	$214.25	$214.25	$214.30
Purchase #3	$240.46	13.328%	$272.5085	$272.51	$272.50	$272.50
Purchase #4	$53.32	5.654%	$56.3347	$56.33	$56.35	$56.30
Purchase #5	$202.92	10.345%	$223.9121	$223.91	$223.90	$223.90
Purchase #6	$146.57	13.509%	$166.3701	$166.37	$166.35	$166.40
Purchase #7	$99.73	5.356%	$105.0715	$105.07	$105.05	$105.10
7 purchase totals =	$1,077.22		$1,176.2576	$1,176.25	$1,176.20	$1,176.30