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	$149.25	13.739%	$169.7555	$169.76	$169.75	$169.80
Purchase #2	$138.77	8.163%	$150.0978	$150.10	$150.10	$150.10
Purchase #3	$24.59	13.871%	$28.0009	$28.00	$28.00	$28.00
Purchase #4	$7.36	6.656%	$7.8499	$7.85	$7.85	$7.80
Purchase #5	$91.61	9.659%	$100.4586	$100.46	$100.45	$100.50
Purchase #6	$70.59	8.153%	$76.3452	$76.35	$76.35	$76.30
Purchase #7	$5.85	9.395%	$6.3996	$6.40	$6.40	$6.40
7 purchase totals =	$488.02		$538.9075	$538.92	$538.90	$538.90