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	$45.63	4.392%	$47.6341	$47.63	$47.65	$47.60
Purchase #2	$17.57	9.537%	$19.2457	$19.25	$19.25	$19.20
Purchase #3	$78.77	8.702%	$85.6246	$85.62	$85.60	$85.60
Purchase #4	$52.27	3.738%	$54.2239	$54.22	$54.20	$54.20
Purchase #5	$202.37	7.123%	$216.7848	$216.78	$216.80	$216.80
Purchase #6	$75.28	13.521%	$85.4586	$85.46	$85.45	$85.50
Purchase #7	$75.80	3.225%	$78.2446	$78.24	$78.25	$78.20
7 purchase totals =	$547.69		$587.2163	$587.20	$587.20	$587.10