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	$6.54	5.853%	$6.9228	$6.92	$6.90	$6.90
Purchase #2	$135.61	6.385%	$144.2687	$144.27	$144.25	$144.30
Purchase #3	$58.81	6.641%	$62.7156	$62.72	$62.70	$62.70
Purchase #4	$150.98	3.816%	$156.7414	$156.74	$156.75	$156.70
Purchase #5	$226.32	11.208%	$251.6859	$251.69	$251.70	$251.70
Purchase #6	$224.87	13.160%	$254.4629	$254.46	$254.45	$254.50
Purchase #7	$78.89	8.764%	$85.8039	$85.80	$85.80	$85.80
7 purchase totals =	$882.02		$962.6012	$962.60	$962.55	$962.60