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	$111.64	13.663%	$126.8934	$126.89	$126.90	$126.90
Purchase #2	$99.53	10.122%	$109.6044	$109.60	$109.60	$109.60
Purchase #3	$81.81	12.577%	$92.0992	$92.10	$92.10	$92.10
Purchase #4	$163.98	3.820%	$170.244	$170.24	$170.25	$170.20
Purchase #5	$198.78	5.112%	$208.9416	$208.94	$208.95	$208.90
Purchase #6	$62.86	13.363%	$71.26	$71.26	$71.25	$71.30
Purchase #7	$93.86	4.285%	$97.8819	$97.88	$97.90	$97.90
7 purchase totals =	$812.46		$876.9245	$876.91	$876.95	$876.90