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	$238.75	11.189%	$265.4637	$265.46	$265.45	$265.50
Purchase #2	$73.79	13.231%	$83.5532	$83.55	$83.55	$83.60
Purchase #3	$186.52	13.827%	$212.3101	$212.31	$212.30	$212.30
Purchase #4	$162.98	5.336%	$171.6766	$171.68	$171.70	$171.70
Purchase #5	$34.70	7.125%	$37.1724	$37.17	$37.15	$37.20
Purchase #6	$148.30	12.770%	$167.2379	$167.24	$167.25	$167.20
Purchase #7	$82.52	9.586%	$90.4304	$90.43	$90.45	$90.40
7 purchase totals =	$927.56		$1,027.8443	$1,027.84	$1,027.85	$1,027.90