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	$177.65	5.421%	$187.2804	$187.28	$187.30	$187.30
Purchase #2	$127.32	8.849%	$138.5865	$138.59	$138.60	$138.60
Purchase #3	$89.78	9.758%	$98.5407	$98.54	$98.55	$98.50
Purchase #4	$184.70	6.577%	$196.8477	$196.85	$196.85	$196.80
Purchase #5	$21.77	3.249%	$22.4773	$22.48	$22.50	$22.50
Purchase #6	$148.88	7.581%	$160.1666	$160.17	$160.15	$160.20
Purchase #7	$92.65	11.771%	$103.5558	$103.56	$103.55	$103.60
7 purchase totals =	$842.75		$907.4550	$907.47	$907.50	$907.50