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	$102.35	9.154%	$111.7191	$111.72	$111.70	$111.70
Purchase #2	$141.75	11.794%	$158.468	$158.47	$158.45	$158.50
Purchase #3	$213.82	3.551%	$221.4127	$221.41	$221.40	$221.40
Purchase #4	$48.51	12.477%	$54.5626	$54.56	$54.55	$54.60
Purchase #5	$234.38	13.211%	$265.3439	$265.34	$265.35	$265.30
Purchase #6	$167.71	4.576%	$175.3844	$175.38	$175.40	$175.40
Purchase #7	$216.76	8.480%	$235.1412	$235.14	$235.15	$235.10
7 purchase totals =	$1,125.28		$1,222.0319	$1,222.02	$1,222.00	$1,222.00