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	$6.96	4.242%	$7.2552	$7.26	$7.25	$7.30
Purchase #2	$96.47	3.612%	$99.9545	$99.95	$99.95	$100.00
Purchase #3	$38.69	3.603%	$40.084	$40.08	$40.10	$40.10
Purchase #4	$205.27	7.131%	$219.9078	$219.91	$219.90	$219.90
Purchase #5	$39.69	9.231%	$43.3538	$43.35	$43.35	$43.40
Purchase #6	$164.79	11.363%	$183.5151	$183.52	$183.50	$183.50
Purchase #7	$106.65	5.159%	$112.1521	$112.15	$112.15	$112.20
7 purchase totals =	$658.52		$706.2225	$706.22	$706.20	$706.40