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	$216.93	3.419%	$224.3468	$224.35	$224.35	$224.30
Purchase #2	$166.86	3.341%	$172.4348	$172.43	$172.45	$172.40
Purchase #3	$78.60	12.539%	$88.4557	$88.46	$88.45	$88.50
Purchase #4	$190.54	4.253%	$198.6437	$198.64	$198.65	$198.60
Purchase #5	$30.27	11.484%	$33.7462	$33.75	$33.75	$33.70
Purchase #6	$150.63	10.866%	$166.9975	$167.00	$167.00	$167.00
Purchase #7	$35.56	5.828%	$37.6324	$37.63	$37.65	$37.60
7 purchase totals =	$869.39		$922.2571	$922.26	$922.30	$922.10