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	$89.92	5.195%	$94.5913	$94.59	$94.60	$94.60
Purchase #2	$70.80	10.747%	$78.4089	$78.41	$78.40	$78.40
Purchase #3	$208.39	5.802%	$220.4808	$220.48	$220.50	$220.50
Purchase #4	$127.34	7.326%	$136.6689	$136.67	$136.65	$136.70
Purchase #5	$187.32	4.738%	$196.1952	$196.20	$196.20	$196.20
Purchase #6	$162.41	9.635%	$178.0582	$178.06	$178.05	$178.10
Purchase #7	$211.34	12.836%	$238.4676	$238.47	$238.45	$238.50
7 purchase totals =	$1,057.52		$1,142.8709	$1,142.88	$1,142.85	$1,143.00