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	$91.65	8.623%	$99.553	$99.55	$99.55	$99.60
Purchase #2	$90.74	11.447%	$101.127	$101.13	$101.15	$101.10
Purchase #3	$37.72	3.351%	$38.984	$38.98	$39.00	$39.00
Purchase #4	$183.32	4.147%	$190.9223	$190.92	$190.90	$190.90
Purchase #5	$102.97	6.534%	$109.6981	$109.70	$109.70	$109.70
Purchase #6	$65.43	9.584%	$71.7008	$71.70	$71.70	$71.70
Purchase #7	$134.58	12.831%	$151.848	$151.85	$151.85	$151.80
7 purchase totals =	$706.41		$763.8332	$763.83	$763.85	$763.80