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	$247.29	13.816%	$281.4556	$281.46	$281.45	$281.50
Purchase #2	$131.72	8.211%	$142.5355	$142.54	$142.55	$142.50
Purchase #3	$145.57	5.720%	$153.8966	$153.90	$153.90	$153.90
Purchase #4	$148.37	3.421%	$153.4457	$153.45	$153.45	$153.40
Purchase #5	$26.83	3.218%	$27.6934	$27.69	$27.70	$27.70
Purchase #6	$183.49	6.539%	$195.4884	$195.49	$195.50	$195.50
Purchase #7	$131.37	5.707%	$138.8673	$138.87	$138.85	$138.90
7 purchase totals =	$1,014.64		$1,093.3825	$1,093.40	$1,093.40	$1,093.40