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	$34.34	10.757%	$38.034	$38.03	$38.05	$38.00
Purchase #2	$70.78	11.295%	$78.7746	$78.77	$78.75	$78.80
Purchase #3	$133.52	5.775%	$141.2308	$141.23	$141.25	$141.20
Purchase #4	$246.61	12.490%	$277.4116	$277.41	$277.40	$277.40
Purchase #5	$118.47	11.280%	$131.8334	$131.83	$131.85	$131.80
Purchase #6	$89.65	8.469%	$97.2425	$97.24	$97.25	$97.20
Purchase #7	$226.53	8.743%	$246.3355	$246.34	$246.35	$246.30
7 purchase totals =	$919.90		$1,010.8624	$1,010.85	$1,010.90	$1,010.70