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	$100.47	8.384%	$108.8934	$108.89	$108.90	$108.90
Purchase #2	$222.56	8.502%	$241.4821	$241.48	$241.50	$241.50
Purchase #3	$208.29	13.808%	$237.0507	$237.05	$237.05	$237.10
Purchase #4	$153.93	6.753%	$164.3249	$164.32	$164.30	$164.30
Purchase #5	$89.94	4.703%	$94.1699	$94.17	$94.15	$94.20
Purchase #6	$90.83	10.735%	$100.5806	$100.58	$100.60	$100.60
Purchase #7	$208.61	9.102%	$227.5977	$227.60	$227.60	$227.60
7 purchase totals =	$1,074.63		$1,174.0993	$1,174.09	$1,174.10	$1,174.20