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	$43.75	13.527%	$49.6681	$49.67	$49.65	$49.70
Purchase #2	$61.64	6.132%	$65.4198	$65.42	$65.40	$65.40
Purchase #3	$167.81	6.353%	$178.471	$178.47	$178.45	$178.50
Purchase #4	$43.64	5.342%	$45.9712	$45.97	$45.95	$46.00
Purchase #5	$96.74	5.319%	$101.8856	$101.89	$101.90	$101.90
Purchase #6	$158.37	3.809%	$164.4023	$164.40	$164.40	$164.40
Purchase #7	$196.40	7.365%	$210.8649	$210.86	$210.85	$210.90
7 purchase totals =	$768.35		$816.6829	$816.68	$816.60	$816.80