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	$172.26	7.816%	$185.7238	$185.72	$185.70	$185.70
Purchase #2	$58.77	6.168%	$62.3949	$62.39	$62.40	$62.40
Purchase #3	$38.33	5.493%	$40.4355	$40.44	$40.45	$40.40
Purchase #4	$91.37	9.371%	$99.9323	$99.93	$99.95	$99.90
Purchase #5	$113.58	10.387%	$125.3776	$125.38	$125.40	$125.40
Purchase #6	$200.43	9.559%	$219.5891	$219.59	$219.60	$219.60
Purchase #7	$225.30	10.703%	$249.4139	$249.41	$249.40	$249.40
7 purchase totals =	$900.04		$982.8671	$982.86	$982.90	$982.80