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	$33.72	10.469%	$37.2501	$37.25	$37.25	$37.30
Purchase #2	$118.91	12.178%	$133.3909	$133.39	$133.40	$133.40
Purchase #3	$177.42	7.533%	$190.785	$190.79	$190.80	$190.80
Purchase #4	$78.93	4.217%	$82.2585	$82.26	$82.25	$82.30
Purchase #5	$29.74	8.473%	$32.2599	$32.26	$32.25	$32.30
Purchase #6	$85.34	6.217%	$90.6456	$90.65	$90.65	$90.60
Purchase #7	$37.37	11.431%	$41.6418	$41.64	$41.65	$41.60
7 purchase totals =	$561.43		$608.2318	$608.24	$608.25	$608.30