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	$146.62	7.519%	$157.6444	$157.64	$157.65	$157.60
Purchase #2	$145.46	11.705%	$162.4861	$162.49	$162.50	$162.50
Purchase #3	$67.83	8.516%	$73.6064	$73.61	$73.60	$73.60
Purchase #4	$105.72	5.796%	$111.8475	$111.85	$111.85	$111.80
Purchase #5	$115.57	3.191%	$119.2578	$119.26	$119.25	$119.30
Purchase #6	$143.83	11.383%	$160.2022	$160.20	$160.20	$160.20
Purchase #7	$102.46	10.187%	$112.8976	$112.90	$112.90	$112.90
7 purchase totals =	$827.49		$897.9420	$897.95	$897.95	$897.90