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	$67.56	7.836%	$72.854	$72.85	$72.85	$72.90
Purchase #2	$90.37	7.815%	$97.4324	$97.43	$97.45	$97.40
Purchase #3	$59.33	6.129%	$62.9663	$62.97	$62.95	$63.00
Purchase #4	$87.82	3.537%	$90.9262	$90.93	$90.95	$90.90
Purchase #5	$16.92	11.349%	$18.8403	$18.84	$18.85	$18.80
Purchase #6	$9.90	5.111%	$10.406	$10.41	$10.40	$10.40
Purchase #7	$70.92	10.397%	$78.2936	$78.29	$78.30	$78.30
7 purchase totals =	$402.82		$431.7188	$431.72	$431.75	$431.70