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	$250.47	8.655%	$272.1482	$272.15	$272.15	$272.10
Purchase #2	$47.72	4.564%	$49.8979	$49.90	$49.90	$49.90
Purchase #3	$162.86	5.848%	$172.3841	$172.38	$172.40	$172.40
Purchase #4	$244.61	5.654%	$258.4402	$258.44	$258.45	$258.40
Purchase #5	$145.72	12.705%	$164.2337	$164.23	$164.25	$164.20
Purchase #6	$52.80	12.301%	$59.2949	$59.29	$59.30	$59.30
Purchase #7	$213.40	9.368%	$233.3913	$233.39	$233.40	$233.40
7 purchase totals =	$1,117.58		$1,209.7903	$1,209.78	$1,209.85	$1,209.70