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	$130.46	9.804%	$143.2503	$143.25	$143.25	$143.30
Purchase #2	$122.90	3.695%	$127.4412	$127.44	$127.45	$127.40
Purchase #3	$26.37	12.732%	$29.7274	$29.73	$29.75	$29.70
Purchase #4	$158.98	10.299%	$175.3534	$175.35	$175.35	$175.40
Purchase #5	$200.25	6.440%	$213.1461	$213.15	$213.15	$213.10
Purchase #6	$175.77	8.117%	$190.0373	$190.04	$190.05	$190.00
Purchase #7	$126.77	4.810%	$132.8676	$132.87	$132.85	$132.90
7 purchase totals =	$941.50		$1,011.8233	$1,011.83	$1,011.85	$1,011.80