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	$98.99	10.108%	$108.9959	$109.00	$109.00	$109.00
Purchase #2	$145.58	13.315%	$164.964	$164.96	$164.95	$165.00
Purchase #3	$61.35	10.188%	$67.6003	$67.60	$67.60	$67.60
Purchase #4	$54.60	9.239%	$59.6445	$59.64	$59.65	$59.60
Purchase #5	$116.81	13.200%	$132.2289	$132.23	$132.25	$132.20
Purchase #6	$213.76	10.215%	$235.5956	$235.60	$235.60	$235.60
Purchase #7	$40.40	3.270%	$41.7211	$41.72	$41.70	$41.70
7 purchase totals =	$731.49		$810.7503	$810.75	$810.75	$810.70