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	$137.82	9.685%	$151.1679	$151.17	$151.15	$151.20
Purchase #2	$40.41	4.165%	$42.0931	$42.09	$42.10	$42.10
Purchase #3	$210.92	10.874%	$233.8554	$233.86	$233.85	$233.90
Purchase #4	$74.75	13.604%	$84.919	$84.92	$84.90	$84.90
Purchase #5	$67.72	6.759%	$72.2972	$72.30	$72.30	$72.30
Purchase #6	$153.85	8.339%	$166.6796	$166.68	$166.70	$166.70
Purchase #7	$237.96	4.800%	$249.3821	$249.38	$249.40	$249.40
7 purchase totals =	$923.43		$1,000.3943	$1,000.40	$1,000.40	$1,000.50