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	$78.64	11.677%	$87.8228	$87.82	$87.80	$87.80
Purchase #2	$20.27	6.163%	$21.5192	$21.52	$21.50	$21.50
Purchase #3	$39.32	4.467%	$41.0764	$41.08	$41.10	$41.10
Purchase #4	$211.54	12.608%	$238.211	$238.21	$238.20	$238.20
Purchase #5	$9.93	3.388%	$10.2664	$10.27	$10.25	$10.30
Purchase #6	$70.36	11.662%	$78.5654	$78.57	$78.55	$78.60
Purchase #7	$131.57	4.419%	$137.3841	$137.38	$137.40	$137.40
7 purchase totals =	$561.63		$614.8453	$614.85	$614.80	$614.90