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	$107.65	9.323%	$117.6862	$117.69	$117.70	$117.70
Purchase #2	$153.87	5.213%	$161.8912	$161.89	$161.90	$161.90
Purchase #3	$238.44	5.121%	$250.6505	$250.65	$250.65	$250.70
Purchase #4	$43.87	5.398%	$46.2381	$46.24	$46.25	$46.20
Purchase #5	$105.35	3.818%	$109.3723	$109.37	$109.35	$109.40
Purchase #6	$53.35	12.118%	$59.815	$59.82	$59.80	$59.80
Purchase #7	$230.39	11.225%	$256.2513	$256.25	$256.25	$256.30
7 purchase totals =	$932.92		$1,001.9046	$1,001.91	$1,001.90	$1,002.00