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	$225.52	5.303%	$237.4793	$237.48	$237.50	$237.50
Purchase #2	$161.94	6.537%	$172.526	$172.53	$172.55	$172.50
Purchase #3	$117.87	7.267%	$126.4356	$126.44	$126.45	$126.40
Purchase #4	$145.82	13.618%	$165.6778	$165.68	$165.70	$165.70
Purchase #5	$169.26	6.818%	$180.8001	$180.80	$180.80	$180.80
Purchase #6	$44.47	4.152%	$46.3164	$46.32	$46.30	$46.30
Purchase #7	$77.46	6.684%	$82.6374	$82.64	$82.65	$82.60
7 purchase totals =	$942.34		$1,011.8726	$1,011.89	$1,011.95	$1,011.80