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	$73.79	11.507%	$82.281	$82.28	$82.30	$82.30
Purchase #2	$153.53	5.571%	$162.0832	$162.08	$162.10	$162.10
Purchase #3	$161.47	8.589%	$175.3387	$175.34	$175.35	$175.30
Purchase #4	$149.79	11.386%	$166.8451	$166.85	$166.85	$166.80
Purchase #5	$12.46	13.140%	$14.0972	$14.10	$14.10	$14.10
Purchase #6	$205.25	11.150%	$228.1354	$228.14	$228.15	$228.10
Purchase #7	$232.47	11.235%	$258.588	$258.59	$258.60	$258.60
7 purchase totals =	$988.76		$1,087.3686	$1,087.38	$1,087.45	$1,087.30