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	$145.46	11.826%	$162.6621	$162.66	$162.65	$162.70
Purchase #2	$181.61	4.259%	$189.3448	$189.34	$189.35	$189.30
Purchase #3	$155.78	5.577%	$164.4679	$164.47	$164.45	$164.50
Purchase #4	$95.89	13.328%	$108.6702	$108.67	$108.65	$108.70
Purchase #5	$170.48	6.591%	$181.7163	$181.72	$181.70	$181.70
Purchase #6	$136.26	7.547%	$146.5435	$146.54	$146.55	$146.50
Purchase #7	$195.86	4.758%	$205.179	$205.18	$205.20	$205.20
7 purchase totals =	$1,081.34		$1,158.5838	$1,158.58	$1,158.55	$1,158.60