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	$13.67	8.325%	$14.808	$14.81	$14.80	$14.80
Purchase #2	$62.67	5.421%	$66.0673	$66.07	$66.05	$66.10
Purchase #3	$113.41	12.651%	$127.7575	$127.76	$127.75	$127.80
Purchase #4	$84.74	5.167%	$89.1185	$89.12	$89.10	$89.10
Purchase #5	$196.46	5.295%	$206.8626	$206.86	$206.85	$206.90
Purchase #6	$203.85	6.533%	$217.1675	$217.17	$217.15	$217.20
Purchase #7	$47.97	10.789%	$53.1455	$53.15	$53.15	$53.10
7 purchase totals =	$722.77		$774.9269	$774.94	$774.85	$775.00