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	$86.26	11.443%	$96.1307	$96.13	$96.15	$96.10
Purchase #2	$19.81	4.744%	$20.7498	$20.75	$20.75	$20.70
Purchase #3	$139.60	4.523%	$145.9141	$145.91	$145.90	$145.90
Purchase #4	$107.39	10.322%	$118.4748	$118.47	$118.45	$118.50
Purchase #5	$159.94	3.525%	$165.5779	$165.58	$165.60	$165.60
Purchase #6	$220.69	10.385%	$243.6087	$243.61	$243.60	$243.60
Purchase #7	$96.63	13.736%	$109.9031	$109.90	$109.90	$109.90
7 purchase totals =	$830.32		$900.3591	$900.35	$900.35	$900.30