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	$225.39	10.619%	$249.3242	$249.32	$249.30	$249.30
Purchase #2	$150.32	8.154%	$162.5771	$162.58	$162.60	$162.60
Purchase #3	$139.82	11.182%	$155.4547	$155.45	$155.45	$155.50
Purchase #4	$230.48	13.464%	$261.5118	$261.51	$261.50	$261.50
Purchase #5	$93.45	6.222%	$99.2645	$99.26	$99.25	$99.30
Purchase #6	$83.28	7.653%	$89.6534	$89.65	$89.65	$89.70
Purchase #7	$80.71	5.107%	$84.8319	$84.83	$84.85	$84.80
7 purchase totals =	$1,003.45		$1,102.6176	$1,102.60	$1,102.60	$1,102.70