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	$128.40	12.119%	$143.9608	$143.96	$143.95	$144.00
Purchase #2	$56.69	11.253%	$63.0693	$63.07	$63.05	$63.10
Purchase #3	$141.62	11.218%	$157.5069	$157.51	$157.50	$157.50
Purchase #4	$224.42	10.710%	$248.4554	$248.46	$248.45	$248.50
Purchase #5	$78.25	5.847%	$82.8253	$82.83	$82.85	$82.80
Purchase #6	$232.62	10.308%	$256.5985	$256.60	$256.60	$256.60
Purchase #7	$219.94	11.186%	$244.5425	$244.54	$244.55	$244.50
7 purchase totals =	$1,081.94		$1,196.9587	$1,196.97	$1,196.95	$1,197.00