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	$135.35	7.576%	$145.6041	$145.60	$145.60	$145.60
Purchase #2	$25.82	4.745%	$27.0452	$27.05	$27.05	$27.00
Purchase #3	$205.53	11.839%	$229.8627	$229.86	$229.85	$229.90
Purchase #4	$204.64	4.420%	$213.6851	$213.69	$213.70	$213.70
Purchase #5	$145.57	11.594%	$162.4474	$162.45	$162.45	$162.40
Purchase #6	$93.27	10.410%	$102.9794	$102.98	$103.00	$103.00
Purchase #7	$120.25	6.254%	$127.7704	$127.77	$127.75	$127.80
7 purchase totals =	$930.43		$1,009.3943	$1,009.40	$1,009.40	$1,009.40