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	$241.60	11.233%	$268.7389	$268.74	$268.75	$268.70
Purchase #2	$29.79	3.281%	$30.7674	$30.77	$30.75	$30.80
Purchase #3	$59.61	10.524%	$65.8834	$65.88	$65.90	$65.90
Purchase #4	$47.99	7.769%	$51.7183	$51.72	$51.70	$51.70
Purchase #5	$170.79	11.298%	$190.0859	$190.09	$190.10	$190.10
Purchase #6	$92.59	7.416%	$99.4565	$99.46	$99.45	$99.50
Purchase #7	$154.52	9.227%	$168.7776	$168.78	$168.80	$168.80
7 purchase totals =	$796.89		$875.4280	$875.44	$875.45	$875.50