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	$184.80	6.262%	$196.3722	$196.37	$196.35	$196.40
Purchase #2	$39.92	11.235%	$44.405	$44.41	$44.40	$44.40
Purchase #3	$13.40	5.286%	$14.1083	$14.11	$14.10	$14.10
Purchase #4	$249.86	6.862%	$267.0054	$267.01	$267.00	$267.00
Purchase #5	$86.26	5.257%	$90.7947	$90.79	$90.80	$90.80
Purchase #6	$104.64	3.264%	$108.0554	$108.06	$108.05	$108.10
Purchase #7	$236.93	7.677%	$255.1191	$255.12	$255.10	$255.10
7 purchase totals =	$915.81		$975.8601	$975.87	$975.80	$975.90