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	$180.38	10.616%	$199.5291	$199.53	$199.55	$199.50
Purchase #2	$200.42	12.666%	$225.8052	$225.81	$225.80	$225.80
Purchase #3	$42.88	9.418%	$46.9184	$46.92	$46.90	$46.90
Purchase #4	$44.49	8.716%	$48.3677	$48.37	$48.35	$48.40
Purchase #5	$37.65	8.296%	$40.7734	$40.77	$40.75	$40.80
Purchase #6	$29.92	4.831%	$31.3654	$31.37	$31.35	$31.40
Purchase #7	$93.90	6.203%	$99.7246	$99.72	$99.70	$99.70
7 purchase totals =	$629.64		$692.4838	$692.49	$692.40	$692.50