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	$185.41	8.330%	$200.8547	$200.85	$200.85	$200.90
Purchase #2	$172.71	6.495%	$183.9275	$183.93	$183.95	$183.90
Purchase #3	$132.55	11.538%	$147.8436	$147.84	$147.85	$147.80
Purchase #4	$116.62	12.844%	$131.5987	$131.60	$131.60	$131.60
Purchase #5	$156.70	11.288%	$174.3883	$174.39	$174.40	$174.40
Purchase #6	$111.78	13.604%	$126.9866	$126.99	$127.00	$127.00
Purchase #7	$160.35	13.866%	$182.5841	$182.58	$182.60	$182.60
7 purchase totals =	$1,036.12		$1,148.1835	$1,148.18	$1,148.25	$1,148.20