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	$30.49	6.639%	$32.5142	$32.51	$32.50	$32.50
Purchase #2	$57.36	4.276%	$59.8127	$59.81	$59.80	$59.80
Purchase #3	$87.98	10.752%	$97.4396	$97.44	$97.45	$97.40
Purchase #4	$19.60	6.720%	$20.9171	$20.92	$20.90	$20.90
Purchase #5	$65.29	3.230%	$67.3989	$67.40	$67.40	$67.40
Purchase #6	$44.90	3.617%	$46.524	$46.52	$46.50	$46.50
Purchase #7	$53.91	5.594%	$56.9257	$56.93	$56.95	$56.90
7 purchase totals =	$359.53		$381.5322	$381.53	$381.50	$381.40