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	$144.66	9.476%	$158.368	$158.37	$158.35	$158.40
Purchase #2	$137.37	4.750%	$143.8951	$143.90	$143.90	$143.90
Purchase #3	$83.74	3.102%	$86.3376	$86.34	$86.35	$86.30
Purchase #4	$40.33	11.783%	$45.0821	$45.08	$45.10	$45.10
Purchase #5	$10.61	4.647%	$11.103	$11.10	$11.10	$11.10
Purchase #6	$62.69	7.415%	$67.3385	$67.34	$67.35	$67.30
Purchase #7	$237.92	5.286%	$250.4965	$250.50	$250.50	$250.50
7 purchase totals =	$717.32		$762.6208	$762.63	$762.65	$762.60