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	$151.76	8.632%	$164.8599	$164.86	$164.85	$164.90
Purchase #2	$160.91	9.803%	$176.684	$176.68	$176.70	$176.70
Purchase #3	$11.83	5.375%	$12.4659	$12.47	$12.45	$12.50
Purchase #4	$129.61	9.452%	$141.8607	$141.86	$141.85	$141.90
Purchase #5	$176.76	10.819%	$195.8837	$195.88	$195.90	$195.90
Purchase #6	$214.50	12.793%	$241.941	$241.94	$241.95	$241.90
Purchase #7	$103.80	11.305%	$115.5346	$115.53	$115.55	$115.50
7 purchase totals =	$949.17		$1,049.2298	$1,049.22	$1,049.25	$1,049.30