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	$175.78	11.755%	$196.4429	$196.44	$196.45	$196.40
Purchase #2	$60.39	13.566%	$68.5825	$68.58	$68.60	$68.60
Purchase #3	$37.94	10.834%	$42.0504	$42.05	$42.05	$42.10
Purchase #4	$171.96	3.683%	$178.2933	$178.29	$178.30	$178.30
Purchase #5	$147.31	12.692%	$166.0066	$166.01	$166.00	$166.00
Purchase #6	$10.64	11.195%	$11.8311	$11.83	$11.85	$11.80
Purchase #7	$245.44	6.860%	$262.2772	$262.28	$262.30	$262.30
7 purchase totals =	$849.46		$925.4840	$925.48	$925.55	$925.50