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	$91.39	5.554%	$96.4658	$96.47	$96.45	$96.50
Purchase #2	$136.92	3.485%	$141.6917	$141.69	$141.70	$141.70
Purchase #3	$139.53	4.557%	$145.8884	$145.89	$145.90	$145.90
Purchase #4	$188.95	8.527%	$205.0618	$205.06	$205.05	$205.10
Purchase #5	$36.89	9.868%	$40.5303	$40.53	$40.55	$40.50
Purchase #6	$137.32	3.867%	$142.6302	$142.63	$142.65	$142.60
Purchase #7	$71.25	13.402%	$80.7989	$80.80	$80.80	$80.80
7 purchase totals =	$802.25		$853.0671	$853.07	$853.10	$853.10