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	$39.26	10.172%	$43.2535	$43.25	$43.25	$43.30
Purchase #2	$6.51	11.828%	$7.28	$7.28	$7.30	$7.30
Purchase #3	$111.73	13.795%	$127.1432	$127.14	$127.15	$127.10
Purchase #4	$246.88	9.260%	$269.7411	$269.74	$269.75	$269.70
Purchase #5	$179.56	9.821%	$197.1946	$197.19	$197.20	$197.20
Purchase #6	$50.46	4.509%	$52.7352	$52.74	$52.75	$52.70
Purchase #7	$103.44	7.766%	$111.4732	$111.47	$111.45	$111.50
7 purchase totals =	$737.84		$808.8208	$808.81	$808.85	$808.80