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	$166.58	11.227%	$185.2819	$185.28	$185.30	$185.30
Purchase #2	$137.65	4.226%	$143.4671	$143.47	$143.45	$143.50
Purchase #3	$41.41	5.795%	$43.8097	$43.81	$43.80	$43.80
Purchase #4	$69.27	10.631%	$76.6341	$76.63	$76.65	$76.60
Purchase #5	$246.89	7.647%	$265.7697	$265.77	$265.75	$265.80
Purchase #6	$158.26	10.276%	$174.5228	$174.52	$174.50	$174.50
Purchase #7	$165.94	12.636%	$186.9082	$186.91	$186.90	$186.90
7 purchase totals =	$986.00		$1,076.3935	$1,076.39	$1,076.35	$1,076.40