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	$185.25	12.233%	$207.9116	$207.91	$207.90	$207.90
Purchase #2	$132.60	13.450%	$150.4347	$150.43	$150.45	$150.40
Purchase #3	$88.25	3.570%	$91.4005	$91.40	$91.40	$91.40
Purchase #4	$12.29	12.148%	$13.783	$13.78	$13.80	$13.80
Purchase #5	$70.25	3.177%	$72.4818	$72.48	$72.50	$72.50
Purchase #6	$137.46	4.253%	$143.3062	$143.31	$143.30	$143.30
Purchase #7	$20.98	13.806%	$23.8765	$23.88	$23.90	$23.90
7 purchase totals =	$647.08		$703.1943	$703.19	$703.25	$703.20