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	$55.52	7.401%	$59.629	$59.63	$59.65	$59.60
Purchase #2	$69.89	3.520%	$72.3501	$72.35	$72.35	$72.40
Purchase #3	$126.26	3.307%	$130.4354	$130.44	$130.45	$130.40
Purchase #4	$32.51	6.790%	$34.7174	$34.72	$34.70	$34.70
Purchase #5	$158.77	3.115%	$163.7157	$163.72	$163.70	$163.70
Purchase #6	$143.92	12.783%	$162.3173	$162.32	$162.30	$162.30
Purchase #7	$97.41	3.165%	$100.493	$100.49	$100.50	$100.50
7 purchase totals =	$684.28		$723.6579	$723.67	$723.65	$723.60