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	$218.53	5.692%	$230.9687	$230.97	$230.95	$231.00
Purchase #2	$136.56	10.758%	$151.2511	$151.25	$151.25	$151.30
Purchase #3	$12.79	12.204%	$14.3509	$14.35	$14.35	$14.40
Purchase #4	$63.60	10.281%	$70.1387	$70.14	$70.15	$70.10
Purchase #5	$211.96	5.603%	$223.8361	$223.84	$223.85	$223.80
Purchase #6	$215.73	10.193%	$237.7194	$237.72	$237.70	$237.70
Purchase #7	$104.27	6.588%	$111.1393	$111.14	$111.15	$111.10
7 purchase totals =	$963.44		$1,039.4042	$1,039.41	$1,039.40	$1,039.40