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	$162.89	5.517%	$171.8766	$171.88	$171.90	$171.90
Purchase #2	$44.40	13.859%	$50.5534	$50.55	$50.55	$50.60
Purchase #3	$182.83	13.830%	$208.1154	$208.12	$208.10	$208.10
Purchase #4	$212.52	9.767%	$233.2768	$233.28	$233.30	$233.30
Purchase #5	$107.93	4.127%	$112.3843	$112.38	$112.40	$112.40
Purchase #6	$200.37	8.620%	$217.6419	$217.64	$217.65	$217.60
Purchase #7	$139.83	3.442%	$144.6429	$144.64	$144.65	$144.60
7 purchase totals =	$1,050.77		$1,138.4913	$1,138.49	$1,138.55	$1,138.50