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	$98.89	10.627%	$109.399	$109.40	$109.40	$109.40
Purchase #2	$16.83	4.773%	$17.6333	$17.63	$17.65	$17.60
Purchase #3	$15.49	5.487%	$16.3399	$16.34	$16.35	$16.30
Purchase #4	$205.44	6.244%	$218.2677	$218.27	$218.25	$218.30
Purchase #5	$126.68	12.419%	$142.4124	$142.41	$142.40	$142.40
Purchase #6	$186.65	5.451%	$196.8243	$196.82	$196.80	$196.80
Purchase #7	$250.56	3.709%	$259.8533	$259.85	$259.85	$259.90
7 purchase totals =	$900.54		$960.7299	$960.72	$960.70	$960.70