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	$148.90	5.716%	$157.4111	$157.41	$157.40	$157.40
Purchase #2	$98.74	6.625%	$105.2815	$105.28	$105.30	$105.30
Purchase #3	$47.96	8.234%	$51.909	$51.91	$51.90	$51.90
Purchase #4	$65.74	9.526%	$72.0024	$72.00	$72.00	$72.00
Purchase #5	$132.79	13.770%	$151.0752	$151.08	$151.10	$151.10
Purchase #6	$165.50	12.279%	$185.8217	$185.82	$185.80	$185.80
Purchase #7	$22.30	7.822%	$24.0443	$24.04	$24.05	$24.00
7 purchase totals =	$681.93		$747.5452	$747.54	$747.55	$747.50