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	$125.26	5.543%	$132.2032	$132.20	$132.20	$132.20
Purchase #2	$239.83	6.608%	$255.678	$255.68	$255.70	$255.70
Purchase #3	$152.94	10.541%	$169.0614	$169.06	$169.05	$169.10
Purchase #4	$138.79	5.117%	$145.8919	$145.89	$145.90	$145.90
Purchase #5	$69.66	4.589%	$72.8567	$72.86	$72.85	$72.90
Purchase #6	$158.38	13.737%	$180.1367	$180.14	$180.15	$180.10
Purchase #7	$159.49	3.150%	$164.5139	$164.51	$164.50	$164.50
7 purchase totals =	$1,044.35		$1,120.3418	$1,120.34	$1,120.35	$1,120.40