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	$151.92	3.183%	$156.7556	$156.76	$156.75	$156.80
Purchase #2	$249.39	10.864%	$276.4837	$276.48	$276.50	$276.50
Purchase #3	$13.55	7.857%	$14.6146	$14.61	$14.60	$14.60
Purchase #4	$55.32	7.668%	$59.5619	$59.56	$59.55	$59.60
Purchase #5	$99.40	4.155%	$103.5301	$103.53	$103.55	$103.50
Purchase #6	$151.93	8.703%	$165.1525	$165.15	$165.15	$165.20
Purchase #7	$198.74	9.366%	$217.354	$217.35	$217.35	$217.40
7 purchase totals =	$920.25		$993.4524	$993.44	$993.45	$993.60