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	$43.34	7.205%	$46.4626	$46.46	$46.45	$46.50
Purchase #2	$203.95	5.410%	$214.9837	$214.98	$215.00	$215.00
Purchase #3	$35.77	13.395%	$40.5614	$40.56	$40.55	$40.60
Purchase #4	$37.34	9.111%	$40.742	$40.74	$40.75	$40.70
Purchase #5	$240.67	7.280%	$258.1908	$258.19	$258.20	$258.20
Purchase #6	$183.47	5.634%	$193.8067	$193.81	$193.80	$193.80
Purchase #7	$241.27	12.666%	$271.8293	$271.83	$271.85	$271.80
7 purchase totals =	$985.81		$1,066.5765	$1,066.57	$1,066.60	$1,066.60