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	$136.79	4.485%	$142.925	$142.93	$142.95	$142.90
Purchase #2	$100.61	13.409%	$114.1008	$114.10	$114.10	$114.10
Purchase #3	$138.76	11.614%	$154.8756	$154.88	$154.90	$154.90
Purchase #4	$143.83	3.208%	$148.4441	$148.44	$148.45	$148.40
Purchase #5	$103.27	4.774%	$108.2001	$108.20	$108.20	$108.20
Purchase #6	$141.51	7.602%	$152.2676	$152.27	$152.25	$152.30
Purchase #7	$179.60	10.206%	$197.93	$197.93	$197.95	$197.90
7 purchase totals =	$944.37		$1,018.7432	$1,018.75	$1,018.80	$1,018.70