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	$139.58	11.627%	$155.809	$155.81	$155.80	$155.80
Purchase #2	$20.34	5.800%	$21.5197	$21.52	$21.50	$21.50
Purchase #3	$162.92	12.183%	$182.7685	$182.77	$182.75	$182.80
Purchase #4	$78.53	3.214%	$81.054	$81.05	$81.05	$81.10
Purchase #5	$34.93	9.104%	$38.11	$38.11	$38.10	$38.10
Purchase #6	$85.54	4.496%	$89.3859	$89.39	$89.40	$89.40
Purchase #7	$141.43	10.786%	$156.6846	$156.68	$156.70	$156.70
7 purchase totals =	$663.27		$725.3317	$725.33	$725.30	$725.40