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	$61.67	9.329%	$67.4232	$67.42	$67.40	$67.40
Purchase #2	$179.32	4.573%	$187.5203	$187.52	$187.50	$187.50
Purchase #3	$33.47	10.789%	$37.0811	$37.08	$37.10	$37.10
Purchase #4	$100.90	10.176%	$111.1676	$111.17	$111.15	$111.20
Purchase #5	$88.77	11.636%	$99.0993	$99.10	$99.10	$99.10
Purchase #6	$184.45	9.427%	$201.8381	$201.84	$201.85	$201.80
Purchase #7	$79.42	7.617%	$85.4694	$85.47	$85.45	$85.50
7 purchase totals =	$728.00		$789.5990	$789.60	$789.55	$789.60