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	$223.57	3.233%	$230.798	$230.80	$230.80	$230.80
Purchase #2	$55.69	5.684%	$58.8554	$58.86	$58.85	$58.90
Purchase #3	$51.32	6.103%	$54.4521	$54.45	$54.45	$54.50
Purchase #4	$127.36	4.522%	$133.1192	$133.12	$133.10	$133.10
Purchase #5	$188.68	13.214%	$213.6122	$213.61	$213.60	$213.60
Purchase #6	$95.87	4.550%	$100.2321	$100.23	$100.25	$100.20
Purchase #7	$35.96	3.850%	$37.3445	$37.34	$37.35	$37.30
7 purchase totals =	$778.45		$828.4135	$828.41	$828.40	$828.40