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	$34.95	10.768%	$38.7134	$38.71	$38.70	$38.70
Purchase #2	$45.80	11.859%	$51.2314	$51.23	$51.25	$51.20
Purchase #3	$115.59	6.430%	$123.0224	$123.02	$123.00	$123.00
Purchase #4	$68.53	6.103%	$72.7124	$72.71	$72.70	$72.70
Purchase #5	$249.56	11.584%	$278.469	$278.47	$278.45	$278.50
Purchase #6	$147.69	3.586%	$152.9862	$152.99	$153.00	$153.00
Purchase #7	$50.55	3.717%	$52.4289	$52.43	$52.45	$52.40
7 purchase totals =	$712.67		$769.5637	$769.56	$769.55	$769.50