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	$62.38	11.250%	$69.3978	$69.40	$69.40	$69.40
Purchase #2	$32.25	9.819%	$35.4166	$35.42	$35.40	$35.40
Purchase #3	$250.43	5.752%	$264.8347	$264.83	$264.85	$264.80
Purchase #4	$248.82	11.123%	$276.4962	$276.50	$276.50	$276.50
Purchase #5	$129.52	7.334%	$139.019	$139.02	$139.00	$139.00
Purchase #6	$233.86	4.189%	$243.6564	$243.66	$243.65	$243.70
Purchase #7	$141.60	6.665%	$151.0376	$151.04	$151.05	$151.00
7 purchase totals =	$1,098.86		$1,179.8583	$1,179.87	$1,179.85	$1,179.80