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	$118.59	10.674%	$131.2483	$131.25	$131.25	$131.20
Purchase #2	$92.62	5.790%	$97.9827	$97.98	$98.00	$98.00
Purchase #3	$186.82	10.215%	$205.9037	$205.90	$205.90	$205.90
Purchase #4	$51.94	11.297%	$57.8077	$57.81	$57.80	$57.80
Purchase #5	$52.61	8.602%	$57.1355	$57.14	$57.15	$57.10
Purchase #6	$60.78	10.358%	$67.0756	$67.08	$67.10	$67.10
Purchase #7	$190.55	4.647%	$199.4049	$199.40	$199.40	$199.40
7 purchase totals =	$753.91		$816.5584	$816.56	$816.60	$816.50