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	$50.93	5.315%	$53.6369	$53.64	$53.65	$53.60
Purchase #2	$79.97	3.773%	$82.9873	$82.99	$83.00	$83.00
Purchase #3	$240.82	5.425%	$253.8845	$253.88	$253.90	$253.90
Purchase #4	$96.83	6.772%	$103.3873	$103.39	$103.40	$103.40
Purchase #5	$78.66	13.445%	$89.2358	$89.24	$89.25	$89.20
Purchase #6	$24.46	9.582%	$26.8038	$26.80	$26.80	$26.80
Purchase #7	$41.47	5.136%	$43.5999	$43.60	$43.60	$43.60
7 purchase totals =	$613.14		$653.5355	$653.54	$653.60	$653.50