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	$145.68	13.583%	$165.4677	$165.47	$165.45	$165.50
Purchase #2	$26.32	8.368%	$28.5225	$28.52	$28.50	$28.50
Purchase #3	$151.53	11.353%	$168.7332	$168.73	$168.75	$168.70
Purchase #4	$184.85	13.258%	$209.3574	$209.36	$209.35	$209.40
Purchase #5	$123.64	12.258%	$138.7958	$138.80	$138.80	$138.80
Purchase #6	$191.45	4.577%	$200.2127	$200.21	$200.20	$200.20
Purchase #7	$103.94	9.152%	$113.4526	$113.45	$113.45	$113.50
7 purchase totals =	$927.41		$1,024.5419	$1,024.54	$1,024.50	$1,024.60