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	$43.83	5.254%	$46.1328	$46.13	$46.15	$46.10
Purchase #2	$91.50	5.152%	$96.2141	$96.21	$96.20	$96.20
Purchase #3	$103.75	12.308%	$116.5196	$116.52	$116.50	$116.50
Purchase #4	$169.45	13.222%	$191.8547	$191.85	$191.85	$191.90
Purchase #5	$129.43	5.415%	$136.4386	$136.44	$136.45	$136.40
Purchase #6	$70.73	13.725%	$80.4377	$80.44	$80.45	$80.40
Purchase #7	$35.84	9.342%	$39.1882	$39.19	$39.20	$39.20
7 purchase totals =	$644.53		$706.7857	$706.78	$706.80	$706.70