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	$99.40	5.461%	$104.8282	$104.83	$104.85	$104.80
Purchase #2	$246.78	9.385%	$269.9403	$269.94	$269.95	$269.90
Purchase #3	$61.53	10.513%	$67.9986	$68.00	$68.00	$68.00
Purchase #4	$204.73	12.107%	$229.5167	$229.52	$229.50	$229.50
Purchase #5	$160.85	11.548%	$179.425	$179.43	$179.45	$179.40
Purchase #6	$100.72	8.595%	$109.3769	$109.38	$109.40	$109.40
Purchase #7	$158.37	4.587%	$165.6344	$165.63	$165.65	$165.60
7 purchase totals =	$1,032.38		$1,126.7201	$1,126.73	$1,126.80	$1,126.60