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	$188.45	6.143%	$200.0265	$200.03	$200.05	$200.00
Purchase #2	$62.70	5.781%	$66.3247	$66.32	$66.30	$66.30
Purchase #3	$238.78	7.583%	$256.8867	$256.89	$256.90	$256.90
Purchase #4	$165.45	10.351%	$182.5757	$182.58	$182.60	$182.60
Purchase #5	$111.31	13.670%	$126.5261	$126.53	$126.55	$126.50
Purchase #6	$211.47	4.410%	$220.7958	$220.80	$220.80	$220.80
Purchase #7	$150.47	7.743%	$162.1209	$162.12	$162.10	$162.10
7 purchase totals =	$1,128.63		$1,215.2564	$1,215.27	$1,215.30	$1,215.20