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	$95.27	4.549%	$99.6038	$99.60	$99.60	$99.60
Purchase #2	$95.79	10.238%	$105.597	$105.60	$105.60	$105.60
Purchase #3	$52.71	12.259%	$59.1717	$59.17	$59.15	$59.20
Purchase #4	$189.94	13.474%	$215.5325	$215.53	$215.55	$215.50
Purchase #5	$10.31	7.250%	$11.0575	$11.06	$11.05	$11.10
Purchase #6	$153.82	13.638%	$174.798	$174.80	$174.80	$174.80
Purchase #7	$196.94	4.288%	$205.3848	$205.38	$205.40	$205.40
7 purchase totals =	$794.78		$871.1453	$871.14	$871.15	$871.20