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	$24.81	5.138%	$26.0847	$26.08	$26.10	$26.10
Purchase #2	$60.61	3.646%	$62.8198	$62.82	$62.80	$62.80
Purchase #3	$171.67	7.832%	$185.1152	$185.12	$185.10	$185.10
Purchase #4	$247.71	4.655%	$259.2409	$259.24	$259.25	$259.20
Purchase #5	$104.35	9.367%	$114.1245	$114.12	$114.10	$114.10
Purchase #6	$74.35	10.480%	$82.1419	$82.14	$82.15	$82.10
Purchase #7	$241.87	13.762%	$275.1561	$275.16	$275.15	$275.20
7 purchase totals =	$925.37		$1,004.6831	$1,004.68	$1,004.65	$1,004.60