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	$16.49	3.756%	$17.1094	$17.11	$17.10	$17.10
Purchase #2	$139.69	4.324%	$145.7302	$145.73	$145.75	$145.70
Purchase #3	$182.76	3.142%	$188.5023	$188.50	$188.50	$188.50
Purchase #4	$110.68	11.109%	$122.9754	$122.98	$123.00	$123.00
Purchase #5	$197.69	6.446%	$210.4331	$210.43	$210.45	$210.40
Purchase #6	$124.70	5.397%	$131.4301	$131.43	$131.45	$131.40
Purchase #7	$179.38	9.604%	$196.6077	$196.61	$196.60	$196.60
7 purchase totals =	$951.39		$1,012.7882	$1,012.79	$1,012.85	$1,012.70