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	$106.38	5.316%	$112.0352	$112.04	$112.05	$112.00
Purchase #2	$233.56	11.240%	$259.8121	$259.81	$259.80	$259.80
Purchase #3	$21.45	13.417%	$24.3279	$24.33	$24.35	$24.30
Purchase #4	$161.29	12.756%	$181.8642	$181.86	$181.85	$181.90
Purchase #5	$219.35	5.117%	$230.5741	$230.57	$230.55	$230.60
Purchase #6	$100.58	11.328%	$111.9737	$111.97	$111.95	$112.00
Purchase #7	$211.68	8.723%	$230.1448	$230.14	$230.15	$230.10
7 purchase totals =	$1,054.29		$1,150.7320	$1,150.72	$1,150.70	$1,150.70