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	$207.54	3.738%	$215.2978	$215.30	$215.30	$215.30
Purchase #2	$6.89	3.699%	$7.1449	$7.14	$7.15	$7.10
Purchase #3	$198.63	3.484%	$205.5503	$205.55	$205.55	$205.60
Purchase #4	$116.32	9.597%	$127.4832	$127.48	$127.50	$127.50
Purchase #5	$6.54	10.629%	$7.2351	$7.24	$7.25	$7.20
Purchase #6	$10.66	13.571%	$12.1067	$12.11	$12.10	$12.10
Purchase #7	$104.78	6.128%	$111.2009	$111.20	$111.20	$111.20
7 purchase totals =	$651.36		$686.0189	$686.02	$686.05	$686.00