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	$65.35	5.340%	$68.8397	$68.84	$68.85	$68.80
Purchase #2	$99.68	11.545%	$111.1881	$111.19	$111.20	$111.20
Purchase #3	$19.96	12.391%	$22.4332	$22.43	$22.45	$22.40
Purchase #4	$41.96	3.568%	$43.4571	$43.46	$43.45	$43.50
Purchase #5	$163.37	11.783%	$182.6199	$182.62	$182.60	$182.60
Purchase #6	$73.73	6.267%	$78.3507	$78.35	$78.35	$78.40
Purchase #7	$140.74	12.786%	$158.735	$158.74	$158.75	$158.70
7 purchase totals =	$604.79		$665.6237	$665.63	$665.65	$665.60