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	$55.85	4.636%	$58.4392	$58.44	$58.45	$58.40
Purchase #2	$230.91	5.730%	$244.1411	$244.14	$244.15	$244.10
Purchase #3	$238.56	6.240%	$253.4461	$253.45	$253.45	$253.40
Purchase #4	$27.87	3.870%	$28.9486	$28.95	$28.95	$28.90
Purchase #5	$246.81	10.128%	$271.8069	$271.81	$271.80	$271.80
Purchase #6	$166.38	11.546%	$185.5902	$185.59	$185.60	$185.60
Purchase #7	$68.32	4.225%	$71.2065	$71.21	$71.20	$71.20
7 purchase totals =	$1,034.70		$1,113.5786	$1,113.59	$1,113.60	$1,113.40