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	$7.69	6.509%	$8.1905	$8.19	$8.20	$8.20
Purchase #2	$158.84	5.135%	$166.9964	$167.00	$167.00	$167.00
Purchase #3	$40.88	7.499%	$43.9456	$43.95	$43.95	$43.90
Purchase #4	$67.53	9.139%	$73.7016	$73.70	$73.70	$73.70
Purchase #5	$175.58	11.815%	$196.3248	$196.32	$196.30	$196.30
Purchase #6	$137.55	9.671%	$150.8525	$150.85	$150.85	$150.90
Purchase #7	$123.60	3.236%	$127.5997	$127.60	$127.60	$127.60
7 purchase totals =	$711.67		$767.6111	$767.61	$767.60	$767.60