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	$130.74	10.397%	$144.333	$144.33	$144.35	$144.30
Purchase #2	$34.81	7.661%	$37.4768	$37.48	$37.50	$37.50
Purchase #3	$81.35	5.765%	$86.0398	$86.04	$86.05	$86.00
Purchase #4	$87.39	10.527%	$96.5895	$96.59	$96.60	$96.60
Purchase #5	$54.71	11.778%	$61.1537	$61.15	$61.15	$61.20
Purchase #6	$52.76	7.231%	$56.5751	$56.58	$56.60	$56.60
Purchase #7	$20.77	10.356%	$22.9209	$22.92	$22.90	$22.90
7 purchase totals =	$462.53		$505.0888	$505.09	$505.15	$505.10