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	$250.48	11.217%	$278.5763	$278.58	$278.60	$278.60
Purchase #2	$9.90	3.452%	$10.2417	$10.24	$10.25	$10.20
Purchase #3	$169.82	11.809%	$189.874	$189.87	$189.85	$189.90
Purchase #4	$78.90	11.482%	$87.9593	$87.96	$87.95	$88.00
Purchase #5	$85.84	4.348%	$89.5723	$89.57	$89.55	$89.60
Purchase #6	$128.46	9.304%	$140.4119	$140.41	$140.40	$140.40
Purchase #7	$189.42	11.176%	$210.5896	$210.59	$210.60	$210.60
7 purchase totals =	$912.82		$1,007.2251	$1,007.22	$1,007.20	$1,007.30