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	$127.50	10.615%	$141.0341	$141.03	$141.05	$141.00
Purchase #2	$165.61	5.228%	$174.2681	$174.27	$174.25	$174.30
Purchase #3	$227.46	3.865%	$236.2513	$236.25	$236.25	$236.30
Purchase #4	$67.71	8.616%	$73.5439	$73.54	$73.55	$73.50
Purchase #5	$26.92	9.815%	$29.5622	$29.56	$29.55	$29.60
Purchase #6	$231.80	4.671%	$242.6274	$242.63	$242.65	$242.60
Purchase #7	$99.25	12.397%	$111.554	$111.55	$111.55	$111.60
7 purchase totals =	$946.25		$1,008.8410	$1,008.83	$1,008.85	$1,008.90