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	$53.26	4.116%	$55.4522	$55.45	$55.45	$55.50
Purchase #2	$108.80	12.187%	$122.0595	$122.06	$122.05	$122.10
Purchase #3	$94.32	11.280%	$104.9593	$104.96	$104.95	$105.00
Purchase #4	$249.35	5.859%	$263.9594	$263.96	$263.95	$264.00
Purchase #5	$111.61	5.372%	$117.6057	$117.61	$117.60	$117.60
Purchase #6	$140.62	9.155%	$153.4938	$153.49	$153.50	$153.50
Purchase #7	$118.66	4.152%	$123.5868	$123.59	$123.60	$123.60
7 purchase totals =	$876.62		$941.1167	$941.12	$941.10	$941.30