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	$221.63	7.670%	$238.629	$238.63	$238.65	$238.60
Purchase #2	$134.70	11.600%	$150.3252	$150.33	$150.35	$150.30
Purchase #3	$167.87	6.371%	$178.565	$178.57	$178.55	$178.60
Purchase #4	$66.56	7.109%	$71.2918	$71.29	$71.30	$71.30
Purchase #5	$134.37	8.274%	$145.4878	$145.49	$145.50	$145.50
Purchase #6	$138.37	11.599%	$154.4195	$154.42	$154.40	$154.40
Purchase #7	$130.33	4.509%	$136.2066	$136.21	$136.20	$136.20
7 purchase totals =	$993.83		$1,074.9249	$1,074.94	$1,074.95	$1,074.90