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	$166.62	11.502%	$185.7846	$185.78	$185.80	$185.80
Purchase #2	$160.69	12.649%	$181.0157	$181.02	$181.00	$181.00
Purchase #3	$117.85	7.683%	$126.9044	$126.90	$126.90	$126.90
Purchase #4	$154.40	12.203%	$173.2414	$173.24	$173.25	$173.20
Purchase #5	$124.51	12.276%	$139.7948	$139.79	$139.80	$139.80
Purchase #6	$146.82	12.282%	$164.8524	$164.85	$164.85	$164.90
Purchase #7	$62.70	5.478%	$66.1347	$66.13	$66.15	$66.10
7 purchase totals =	$933.59		$1,037.7280	$1,037.71	$1,037.75	$1,037.70