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	$188.80	7.616%	$203.179	$203.18	$203.20	$203.20
Purchase #2	$52.98	12.599%	$59.655	$59.66	$59.65	$59.70
Purchase #3	$103.90	10.584%	$114.8968	$114.90	$114.90	$114.90
Purchase #4	$178.75	3.274%	$184.6023	$184.60	$184.60	$184.60
Purchase #5	$143.70	5.132%	$151.0747	$151.07	$151.05	$151.10
Purchase #6	$12.67	9.613%	$13.888	$13.89	$13.90	$13.90
Purchase #7	$176.31	13.155%	$199.5036	$199.50	$199.50	$199.50
7 purchase totals =	$857.11		$926.7994	$926.80	$926.80	$926.90