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	$103.70	12.231%	$116.3835	$116.38	$116.40	$116.40
Purchase #2	$16.72	4.525%	$17.4766	$17.48	$17.50	$17.50
Purchase #3	$76.46	7.502%	$82.196	$82.20	$82.20	$82.20
Purchase #4	$155.31	3.549%	$160.822	$160.82	$160.80	$160.80
Purchase #5	$115.76	13.674%	$131.589	$131.59	$131.60	$131.60
Purchase #6	$112.55	13.607%	$127.8647	$127.86	$127.85	$127.90
Purchase #7	$64.48	9.239%	$70.4373	$70.44	$70.45	$70.40
7 purchase totals =	$644.98		$706.7691	$706.77	$706.80	$706.80