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	$238.97	12.728%	$269.3861	$269.39	$269.40	$269.40
Purchase #2	$239.47	5.606%	$252.8947	$252.89	$252.90	$252.90
Purchase #3	$154.76	4.698%	$162.0306	$162.03	$162.05	$162.00
Purchase #4	$80.80	6.460%	$86.0197	$86.02	$86.00	$86.00
Purchase #5	$141.81	12.721%	$159.8497	$159.85	$159.85	$159.80
Purchase #6	$28.38	7.326%	$30.4591	$30.46	$30.45	$30.50
Purchase #7	$88.88	13.188%	$100.6015	$100.60	$100.60	$100.60
7 purchase totals =	$973.07		$1,061.2414	$1,061.24	$1,061.25	$1,061.20