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	$173.33	7.248%	$185.893	$185.89	$185.90	$185.90
Purchase #2	$38.82	9.724%	$42.5949	$42.59	$42.60	$42.60
Purchase #3	$198.77	8.357%	$215.3812	$215.38	$215.40	$215.40
Purchase #4	$51.93	11.315%	$57.8059	$57.81	$57.80	$57.80
Purchase #5	$37.54	13.152%	$42.4773	$42.48	$42.50	$42.50
Purchase #6	$37.69	5.712%	$39.8429	$39.84	$39.85	$39.80
Purchase #7	$107.60	7.394%	$115.5559	$115.56	$115.55	$115.60
7 purchase totals =	$645.68		$699.5511	$699.55	$699.60	$699.60