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	$85.65	3.151%	$88.3488	$88.35	$88.35	$88.30
Purchase #2	$73.76	6.176%	$78.3154	$78.32	$78.30	$78.30
Purchase #3	$194.42	10.629%	$215.0849	$215.08	$215.10	$215.10
Purchase #4	$156.98	10.238%	$173.0516	$173.05	$173.05	$173.10
Purchase #5	$66.46	6.762%	$70.954	$70.95	$70.95	$71.00
Purchase #6	$19.81	3.788%	$20.5604	$20.56	$20.55	$20.60
Purchase #7	$27.53	3.264%	$28.4286	$28.43	$28.45	$28.40
7 purchase totals =	$624.61		$674.7437	$674.74	$674.75	$674.80