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	$249.52	5.186%	$262.4601	$262.46	$262.45	$262.50
Purchase #2	$50.44	4.253%	$52.5852	$52.59	$52.60	$52.60
Purchase #3	$233.34	4.104%	$242.9163	$242.92	$242.90	$242.90
Purchase #4	$189.87	4.269%	$197.9756	$197.98	$198.00	$198.00
Purchase #5	$33.94	13.464%	$38.5097	$38.51	$38.50	$38.50
Purchase #6	$129.91	7.231%	$139.3038	$139.30	$139.30	$139.30
Purchase #7	$48.72	9.609%	$53.4015	$53.40	$53.40	$53.40
7 purchase totals =	$935.74		$987.1522	$987.16	$987.15	$987.20