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	$143.58	5.390%	$151.319	$151.32	$151.30	$151.30
Purchase #2	$248.98	4.642%	$260.5377	$260.54	$260.55	$260.50
Purchase #3	$153.27	12.765%	$172.8349	$172.83	$172.85	$172.80
Purchase #4	$117.34	5.463%	$123.7503	$123.75	$123.75	$123.80
Purchase #5	$157.32	9.423%	$172.1443	$172.14	$172.15	$172.10
Purchase #6	$90.90	5.632%	$96.0195	$96.02	$96.00	$96.00
Purchase #7	$165.84	11.424%	$184.7856	$184.79	$184.80	$184.80
7 purchase totals =	$1,077.23		$1,161.3913	$1,161.39	$1,161.40	$1,161.30