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	$111.98	10.254%	$123.4624	$123.46	$123.45	$123.50
Purchase #2	$99.26	13.359%	$112.5201	$112.52	$112.50	$112.50
Purchase #3	$179.50	3.483%	$185.752	$185.75	$185.75	$185.80
Purchase #4	$93.87	9.518%	$102.8045	$102.80	$102.80	$102.80
Purchase #5	$249.40	5.520%	$263.1669	$263.17	$263.15	$263.20
Purchase #6	$71.85	7.794%	$77.45	$77.45	$77.45	$77.50
Purchase #7	$98.72	8.802%	$107.4093	$107.41	$107.40	$107.40
7 purchase totals =	$904.58		$972.5652	$972.56	$972.50	$972.70