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	$131.45	11.595%	$146.6916	$146.69	$146.70	$146.70
Purchase #2	$16.77	8.845%	$18.2533	$18.25	$18.25	$18.30
Purchase #3	$162.93	6.481%	$173.4895	$173.49	$173.50	$173.50
Purchase #4	$72.95	12.571%	$82.1205	$82.12	$82.10	$82.10
Purchase #5	$35.81	13.214%	$40.5419	$40.54	$40.55	$40.50
Purchase #6	$237.43	12.213%	$266.4273	$266.43	$266.45	$266.40
Purchase #7	$221.99	5.780%	$234.821	$234.82	$234.80	$234.80
7 purchase totals =	$879.33		$962.3451	$962.34	$962.35	$962.30