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	$132.36	11.803%	$147.9825	$147.98	$148.00	$148.00
Purchase #2	$190.32	5.758%	$201.2786	$201.28	$201.30	$201.30
Purchase #3	$95.30	10.852%	$105.642	$105.64	$105.65	$105.60
Purchase #4	$86.68	13.729%	$98.5803	$98.58	$98.60	$98.60
Purchase #5	$244.70	10.154%	$269.5468	$269.55	$269.55	$269.50
Purchase #6	$132.48	7.204%	$142.0239	$142.02	$142.00	$142.00
Purchase #7	$141.87	11.393%	$158.0332	$158.03	$158.05	$158.00
7 purchase totals =	$1,023.71		$1,123.0873	$1,123.08	$1,123.15	$1,123.00