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	$169.54	13.375%	$192.216	$192.22	$192.20	$192.20
Purchase #2	$33.82	10.257%	$37.2889	$37.29	$37.30	$37.30
Purchase #3	$95.92	10.382%	$105.8784	$105.88	$105.90	$105.90
Purchase #4	$116.26	4.124%	$121.0546	$121.05	$121.05	$121.10
Purchase #5	$119.77	11.555%	$133.6094	$133.61	$133.60	$133.60
Purchase #6	$127.84	5.829%	$135.2918	$135.29	$135.30	$135.30
Purchase #7	$105.25	5.810%	$111.365	$111.37	$111.35	$111.40
7 purchase totals =	$768.40		$836.7041	$836.71	$836.70	$836.80