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	$40.93	6.103%	$43.428	$43.43	$43.45	$43.40
Purchase #2	$81.63	4.345%	$85.1768	$85.18	$85.20	$85.20
Purchase #3	$174.77	12.671%	$196.9151	$196.92	$196.90	$196.90
Purchase #4	$23.80	3.608%	$24.6587	$24.66	$24.65	$24.70
Purchase #5	$49.54	10.151%	$54.5688	$54.57	$54.55	$54.60
Purchase #6	$128.69	6.448%	$136.9879	$136.99	$137.00	$137.00
Purchase #7	$126.89	4.730%	$132.8919	$132.89	$132.90	$132.90
7 purchase totals =	$626.25		$674.6272	$674.64	$674.65	$674.70